Diving into a new Draft format can be intimidating, but I'm here to help! Guilds of Ravnica has hit the scene, and I'm going to break down what you should be looking for as you crack your first few packs. I'll talk a little about each guild's strategy, then go over each tier of card, which will help inform your direction in Draft.
The typical Boros deck is all about attacking. Mentor rewards you for curving out, and Boros is looking to pair aggressive creatures with combat tricks and removal to kill the opponent before they get their game plan going. If you see a Boros-colored card in a high tier and wonder why, it's likely because Boros values aggressive cards.
Surveil is the name of the game here, which leads Dimir decks down a controlling path. There are plenty of surveil cards and cards that reward you for surveilling, so it's a well-supported archetype that has a lot of high-tier cards.
The goal of Golgari decks is to trade off creatures and fuel undergrowth, but this theme isn't as well supported as some of the other guilds. As such, the best Golgari cards tend to be the ones that are good in a vacuum and not as heavily into undergrowth.
Normally a controlling color pair, Izzet in this set is much more aggressive. Jump-start is found on beatdown cards like Sonic Assault and Maximize Altitude, so keep that in mind when looking at the powerful Izzet cards.
Convoke is back, and it's less focused on tokens than just curving out. Selesnya doesn't go quite as wide as before, but is still a great deck, and convoke cards got high ratings as a result.
Now that we know what the guilds are doing, let's get into the tiers:
Best of the Best
These are the windmill slam pack 1, pick 1 cards; they are what you join a draft hoping to see. Most are powerful in a vacuum, but even the ones that play into guild themes are so good when you get there that you should take them first and go for it.
Best of the Rest
These are cards you will be very happy to open. They aren't necessarily cards that will define your deck quite as much as the tier above, but you'll almost never pass on one of these, and they are a great start to a draft.
This tier is made up of cards that are above-average first picks. You don't get up and run around the table when you pick one, but starting with a premium removal spell or powerful threat is always a good sign. A lot of guild-themed cards are here, and if your deck ends up supporting them well, they can easily be among the best cards in your deck.
These cards are exactly below the line where you're happy first-picking them. They will always make the cut, and you will be glad to play them, but they lack the power of the higher tiers.
You can't finish a draft deck without cards from this category. They are the building blocks, the creatures and spells that fill out your deck, even if you're unhappy taking them early. You'll play plenty of these cards, you just hope to take them picks 5+.
Here's to hoping you start at the top of the list in your next draft. Good luck!