Red Deck Wins
As such, RDW is often a coin-flip of a deck. You can either explosively win the game by as early as Turn 3, or you can blow out and stall into a painful defeat. Often times there isn't much of a middle ground. This is due to the hyper-aggressive nature of the deck, which limits the deck's stability going into the mid and late game.
How to RDW
When playing a RDW deck, do not be afraid to mulligan your hand if it's not explosive enough. Remember, you want them dead ASAP; every turn they get to live is a turn they have to stall you out. Also keep in mind that your answers to the opponent's threats are going to be limited, as you need your burn spells to finish them off more often than not, and any other kind of removal is going to slow you down. The deck is rather easy to learn and not very difficult to master, but it certainly is not auto-pilot and you need to think about how you're going to kill your opponent with as few cards as possible.
To effectively play this deck, you're going to need to know exactly what cards your opponent can use against you. Failure to do so can result in getting blown out by over-extending or not going hard enough. Also, if the opponent is playing a White-based deck (or Green and Black in some cases) make sure you're packing some way to negate Lifegain. When building RDW, always start with 4x Lightning Bolt or some kind of equivalent for the format you're in, and 4x of the cheapest most aggressive creature you can find (Goblin Guide for example, any 2/X with Haste for R is good). From there expand into similar cards, leaning more on burn or aggro depending on what decks you plan to face. For example, when facing a control deck go for the burn, as this will make their beloved creature removal useless and will force them to rely on counterspells which tend to be far less efficient. Troll the fuck out of Blue players by playing Pyroblast and Red Elemental Blast. Fireblast is always a solid choice; the ability to sac 2 mountains even when tapped out to push that last crucial 4 damage or wipe some cunt creature that is screwing you cannot be underestimated.
How to Deal with RDW
When playing against a RDW deck, your goal is to stall them out. If you're not dead or close to death by Turn 5, you're probably going to win. Try to stay above 5 Life if you can and keep their creatures at bay by either making them useless (big bodies) or killing them outright. Most sweepers are going to be too slow so keep removal efficient and under 4 Mana. This is also one of the few matchups where copious Lifegain Spells are going to be a boon, but straight up Lifegain should be avoided; utilize cards that do something and give you Life as a bonus. Any cheap wall that somehow gains you Life is also going to be tremendously helpful as they'll be forced to slow down by either killing it with a burn spell and a blocked attack or by having to only use burn spells to kill you. Do not try to damage race them.
If you are a creature-based deck, be conservative early and make sure you have 2 blockers for every one attacker they have to avoid getting blown out by Haste and block-denial. By Turn 4 you should be able to start powering them out with your much more powerful threats. When building to fuck a RDW in the ass start with 4x of some kind of cheap 1-2 Mana blocker, like Wall of Omens/Wall of Blossoms. Then find 4x of a card that gains life for a relevant effect, such as drawing cards, generating blockers, or removing creatures, such as Timely Reinforcements or Lightning Helix. From there find a powerful threat that can gain you a good shot in the arm of Life in the 3-5 mana range, such as Thragtusk, and jam 3-4 copies. After developing the core, make sure you cover your bases with other cheap removal (Swords to Plowshares/Path to Exile, Pyroclasm, Lightning Bolt), damage prevention/negation (Fog, blockers), and some of your own relevant 3-5 mana threats with 2-3 late game powerhouses.