Today's article is a general strategy article aimed at strengthening one specific area of your game – how to identify when you should deviate from the typical rule of thumb in a given situation.
Magic is a very complex game. To manage this complexity, we use shortcuts and rules of thumb that hold for the most part and apply to a wide range of similar situations. For instance, as a rule you want to tap your basic lands first while leaving your dual lands untapped. Most of the time this is correct since it affords you the most options as far as what combinations of mana you can produce from your remaining lands. Players are generally pretty good at understanding and applying these types of rules of thumb – especially at the more competitive levels of play – but a tougher skill that is much harder to develop is knowing when it's correct to deviate from a particular rule of thumb.
Let's start by considering the example just mentioned.
As a general rule, if you have a combination of lands, some of which are basic lands and others of which have abilities or produce multiple colors, you want to use the basic lands first so that the more versatile lands are left untapped. This allows you to cast or at least represent more things. For instance, if you have one Swamp, one Forest and one Blooming Marsh on the battlefield and you cast Winding Constrictor, it is generally better to tap your two basic lands and leave the Blooming Marsh untapped. This allows you to represent both Fatal Push and Blossoming Defense. Even if you don't have either of those cards in your hand, leaving the appropriate mana untapped and available to you may cause your opponent to make a play that is less good against you because they are trying to play around one of those two cards.
There are a few exceptions to this rule. One is if your opponent is playing land destruction such as Field of Ruin. In this case you often want to tap your non-basic land first so that when the opponent activates their Field of Ruin, they leave you with an extra untapped land since you left your dual land tapped instead of untapped. The easiest way to identify this situation is if the opponent has a Field of Ruin on the battlefield, but you also want to think about what would happen if the opponent plays a Field of Ruin on their next turn and immediately activates it. Given the high number of Field of Ruins being played in both Standard and Modern right now, this is an important exception to identify.
Another exception is when you don't want the opponent to play around the card you would otherwise be representing. For instance, if you want the opponent to cast a main phase removal spell on your Winding Constrictor, perhaps because you didn't draw any cards that grant +1/+1 counters or because you are about to cast a more important creature the following turn or maybe you have a way in your hand to Reanimate the Snake. Whatever the reason, if you would rather the opponent not play around the card, then you want to tap your mana such that you are not representing the card you don't want them to play around. In other words, leave the Swamp untapped instead of the Blooming Marsh if you don't want the opponent to play around Blossoming Defense.
As a general rule, you want to play your spells post-combat rather than pre-combat. There are two main reasons for this. The first is that it leaves your options open. For instance, if the opponent plays a bounce spell on your creature during combat, maybe you would rather replay the bounced creature this turn instead of playing the other card in your hand. But if you already used your mana to cast the other card in hand pre-combat, then you wouldn't be able to replay the bounced creature post-combat. The other main reason is because it limits the amount of information your opponent has in which to make their decisions in combat. For instance, if you play your better creature pre-combat and then attack, maybe the opponent takes the damage and kills your better creature you just played, whereas if you attacked first they would have killed your attacker and then your better creature would still be around.
The most straightforward exception to this rule is when the pre-combat spell is relevant to combat. For instance, if you have an aura or equipment spell that you can use to enhance your attacking creature's stats, you want to play it before combat. Similarly if you are casting a haste creature, but these are the more obvious exceptions to this rule.
A less obvious exception has to do with gaining information. For instance, if you have a Sorcerous Spyglass or a Divination that you plan on casting this turn, it's usually correct to cast it pre-combat to give yourself access to the most information possible to make your combat decisions. For instance, if you cast Divination and draw two more creatures, each of which is more important than the creature you have on the battlefield, then this information will suggest that it's correct to attack into the opponent's Seal Away, but if instead you draw into a pair of Blossoming Defenses that you don't have the mana to cast this turn, then that information will suggest that you want to stay back this turn and instead attack next turn when you have mana available to cast your protection spells. By casting Sorcerous Spyglass pre-combat you gain access to information about what the opponent has in hand and you can thereby make a more informed decision as to which creatures to attack with. For instance, if you see that they do not have Settle the Wreckage in hand, then it's safe to attack all out whereas if you see they do have it maybe you attack with only two of your three creatures.
The newest variant of this type of card is Navigator's Compass. It fixes your mana at the expense of putting you down a card. In other words, it doesn't replace itself or trade with an opposing card, in contrast to a card like Prophetic Prism which replaces itself while fixing your mana and is therefore usually a card you should play. As a general rule, you should not play with Navigator's Compass or other mana fixers that leave you down a card.
An exception to this rule is when you are in a desperate situation and/or have an Abundance of synergies with the card. For instance, if your deck is both full of "historic matters" cards and deficient in historic cards to turn on all these historic matters cards, then sometimes it's correct to swallow your pride and play the Navigator's Compass.
Another exception to this rule – which doesn't so much apply to Navigator's Compass as it does to previous variants of the card – is when your deck both has bad mana fixing and has several ways to Recoup the card disadvantage generated by the artifact fixer, in addition to having steep mana requirements. For example, back in Alara block one time I drafted a five-color control deck, which was a very common and powerful archetype in the format, but I ended up with really weak mana fixing. The power level of my cards was very high, containing multiple sweepers, several removal spells, multiple ways to generate card advantage and a few bomb win conditions. The problem was that these cards were spread out among all five colors and my mana fixing was lacking. So I played a copy of Mana Cyclix in my deck in order to help me to cast my spells. The card disadvantage it created (it's basically a one-mana Prophetic Prism that doesn't draw a card) was mitigated by all the card advantage the other spells in my deck produced. It was correct for that particular deck because that deck had a glaring weakness – it was unable to produce all the colors of mana to cast its cards – while being strong at coming back from being down a card via its removal, sweepers and card advantage spells. Thus Mana Cylix for that specific deck was a perfect fit. In general, you never want to play with these types of cards, but it's important to identify when it's correct to play a card that is almost never worth playing.
As a general rule, you almost always want to play exactly 40 cards in Limited because it maximizes your chances of drawing your best cards. I've heard arguments for playing 41 cards in decks that want 16.5 lands and 23.5 spells, and it may be barely correct to do so (or perhaps barely incorrect to do so) in most of these cases, but I think even in these scenarios I would not recommend deviating from the rule of always playing the minimum (i.e. exactly 40) cards in Limited, whether Sealed Deck or Booster Draft.
The one exception to this rule that you should be aware of is when playing against an opponent that is trying to win by decking you. In this situation, it is generally best to sideboard in every card that is remotely playable in your colors as well as enough basic lands to maintain your mana to spell ratio. For instance, if you have six playable cards in your colors in your sideboard, bring them in along with four additional basic lands. This will make your starting library 50 cards and will thereby likely buy you an extra turn or two to kill the opponent. Games against mill strategies play out very differently than normal games of Limited. You're essentially on a clock to kill your opponent before your library runs out, of cards so the number of cards in your library is your vital resource rather than your life total.
The reason you don't want to bring in something like 300 basic lands is because then you will only draw one or two spells throughout the game and the opponent will thereby have the luxury to kill you with incidental damage. Instead you want to keep your deck's mana to spell ratio the same but to make its size just a little bit bigger to buy you those extra two turns to finish off the opponent before they would otherwise deck you. In many cases those extra few cards in your library will be the difference between a win and a loss whereas drawing a weaker card that you boarded in will only rarely cost you a game against a mill strategy that you otherwise would have won, assuming of course the card boarded in is in fact remotely playable.
Magic is a complex game and one important way to excel at it is to understand and apply various rules of thumb such as the ones mentioned here today. Once you understand these rules of thumb, however, there is yet another important skill to develop to take your game that much further, namely to be able to identify when it's best to deviate from a general rule. The examples provided today should help you to identify the specific cases mentioned, namely (1) when to tap mana in an unconventional way, (2) when to cast spells pre-combat, (3) when to play mana fixers that yield card disadvantage, and (4) when to play more than 40 cards in Limited. More importantly, however, they should also help show you the method by which to examine all the other rules of thumb that are the basis of many of your decisions in a game of Magic.
To maximally benefit from this article, I encourage you to write down all the rules of thumb you use in making decisions in matches of Magic and to then try to come up with scenarios for when you should deviate from those rules. By doing this, you will train yourself to identify exceptions to the rule and thereby take your game to a level you may not have previously known possible.