Okay I joked a bit in the big thread, but then I realized that IPA draft was one of the formats. When I say I owned this format, I mean it. My record was winning 13 IPA 8-player drafts in a row (and many dozens of others that weren't consecutive). During this era I drafted two or more times every day for a couple months (and mind you this was pre-MtGO). So I know of what I speak in the realm of IPA drafting.
First things first, there are six cards in Invasion, Planeshift and Apocalypse which, if you see them in a pack, you must pick them and play colors to support them. It's a very easy to remember list:
Crosis
Treva
Rith
Darigaaz
Dromar
Spiritmonger
There is literally no other card which is a better pick in any situation than these. Fact or Fiction might seem like a great first pick, but if you are passing a dragon, it is not and you will regret it.
There are two archetypes in IPA draft which are a cut above the others. The first is Red-Black-Blue, and is pretty much the premiere archetype. Agonizing Demise, Terminate, Recoil, Fire // Ice, Jilt, etc. You will not get a better suite of removal in any other set of colors.
The second strongest archetype is Red-Black-Green. Ordinarily you end up in RBG when you start off as RB (which is very typical with a first pick Agonizing Demise or something) and don't get Recoils, Fact or Fictions or Repulses. Green gives you some top-flight creatures (especially from Planeshift where the Red/Green multicolor stuff is quite strong) and a potentially stronger pool in Apocalypse, where you'll have access to the amazing Consume Strength. Also, if you end up seeing a Spiritmonger or Pernicious Deed, you'll have a huge pull in this direction.
A note on removal - unlike many blocks, removal is quite easy to come by in IPA. However, the quality is widely divergent. Agonizing Demise vs. Plague Spores is the classic example of this. Now, Plague Spores is an absolutely playable card. However, you should not be first picking it except in a very poor pack. Demise, on the other hand, is a strong first pick. Kicked, it has the same mana cost as Plague Spores, but its other qualities make it exceptional. IPA is a format with enormous creatures and long standstills. Agonizing Demise pierces that in all the ways Plague Spores does not. Pay very close attention to how good the removal you are picking is. It is better to spend your early picks getting top-flight creatures (even utility creatures) than it is to get low-quality removal when there is so much of that available.
A note on Domain - don't do it. There is basically one reason to play Domain, and that is if you open Collective Restraint and the pack supports very little else. You may be inclined to try a five color deck so that you may pick and choose the best cards, as can be done in Alara block drafting, but IPA 5-color is not the same beast as Alara 5-color. In order to make domain truly work in draft you need a significant number of bombtastic threats. The powerhouses of Domain are strong, but few of them are unanswerable. So you lose a significant amount of speed in your deck while you spend early turns setting up your mana base and you wind up with creatures that are no less susceptible to Terminate than those of your opponent - and chances are you didn't get as many Terminates as they did.
What to do when you're not playing one of the two best decks? Obviously not everyone can play RGB or UBR. All those white cards have to wind up somewhere (not to mention the white/blue and white/green cards). Let me restate that you do not want this person to be you (unless you opened a Dragon of an appropriate color scheme). Do not go into a draft desiring to play white in IPA. Understand how to react when it does happen, but never try for it. When you're playing with white, you have one major advantage, and that is that you can ignore some of the strongest picks in the block and the strongest picks for you will likewise get ignored by the majority of the table. The key is to quickly determine what is most open among red, black, and blue. Green has a lot of depth without a huge amount of diversity in the first pack so don't worry about that for now. If you're stuck with white (maybe you opened a poor pack that had a Rout in it), you want to be trying to end up in White-Blue-Black or White-Red-Green. The latter is the more difficult of the two because you only have one color from which to get your removal. The value of cards like Magma Burst goes up exponentially here. When you're in WRG, you can expect to end up playing mediocre cards like Manacles of Decay for lack of better options. White-Blue-Black has a bit more quality to it, but only if you get the significant card advantage powerhouses available to you. It's very common to attempt White-Blue-Black and feel like things are going well through Invasion only to realize that you've got almost no quality black cards and you've wound up playing White-Blue-Green. In case it wasn't obvious, that's A Bad Thing.
A brief note on WGU. Unless you opened a Treva, you want to avoid this combination at all costs. In a world of abundant removal, you will have found the one deck that can't get threats off the board reliably. You're also stuck with arguably the weakest color set in Apocalypse. Although cards like Mystic Snake are powerhouses of the Constructed world, they don't break draft games wide open. On the few occasions I was unlucky enough to open a Treva, I usually made myself attempt a five-color mess rather than play WGU. The possbility of accelerating into an early fatty and backing it up with a bit of countermagic was usually my only real win condition.
So what about the enemy color tris? Why not play White-Green-Black and take advantage of the enormously powerful cards from Apocalypse? Why note play White-Blue-Red and pack your deck with things like Jilt, Lightning Angel, Goblin Trenches, etc? The answer is simple - because there are two packs to get through first and because playing an enemy tri is not the only reason to desire those cards. If you attempt to play an enemy tri early, you end up severely limiting your card choice through the first two packs for a chance at greater rewards in pack three. There was another draft which had a similar situation - Selesnya/Simic/Azorius decks in RGD drafting. You skip out on Guildpact entirely in order to maximize your card choice in Dissension. That didn't work either. When thinking about strong draft archetypes through history, the strongest are those which have the deepest pools. If you limit yourself in any given pack, you are betting the whole affair on the slim chance that the stars align perfectly in pack three. That's never the right way to win.
A few final reminders:
1) During Invasion, keep Gating in mind. CitP-effect creatures are exceptionally strong due to the high power level on gating creatures. Nightscape Battlemage isn't an enormously powerful card on its own, but when you have a Cavern Harpy to back it up, it can break stalemates wide open.
2) Assume that everyone else is playing Red/Black/Blue. When you look at a pack, be confident that every quality RBU card from that pack will be gone by the next time you see it.
3) Flagbearers are an enormous pain in the ass, but that doesn't make them good. Make sure your deck or sideboard has evasion creatures (especially Fear creatures) which can get past the incredibly boring power of WUG.
4) Make sure you're using every one of your colors for its strengths. If you're playing blue, make sure you get some bounce in addition to card draw. If you're playing green, make sure you get some artifact/enchantment removal (even if you have to splash a white source to make a Wax/Wane full strength). The opposite is true as well. If you're playing blue, you shouldn't be relying on black and red to provide you with card draw or flying creatures. Don't be afraid to make your deck a 33/33/33 split. Playing two colors with a small splash might seem better but this is a draft where card quality is everything and where games can often go long. Play the better cards even if it means your deck is a little slower.
