There is a hero pack, 4 four card packs, 3 five card packs, and 3 six card packs. You can open them in any order. It's unanimous that you should open the hero pack first so you know which cards synergize with your hero. It's also mostly unanimous that you should open the biggest packs last so that you have more choices in order to figure out what things your deck is missing in the last few picks. I think common knowledge is wrong though, because if you open a 6 pack it's highly likely there will be a god tier card that you will be forced to windmill slam even if it is unrelated to the specific needs of your deck, and it's more likely a 4 pack will let you choose between mediocre cards and it's better to know later on whether you need a mediocre attacker or a mediocre blocker.
All the cards are fully upgraded, the cost is right on the card. Sometimes you will get offered the chance to get another copy of the same card. When you get that opportunity, the second copy of the card is one level worse.
Lots of draft games go to attrition, few of them are won by a player that rushdowns the other guy. You want to prioritize cards that make your overall deck quality better like green cards a lot. But if you go too overboard with that it is possible to die.
Dowager Anibaldo, Shofet Daru, and Doge Monteferro are the best three heroes by a decent margin IMO. Ashbar Akar is almost as good as those guys, but not quite on their level. Brigand Lucca and Xalia are both awful IMO. Be sure to not let Brigand steal stuff from you when you fight him even if that means skipping your own draws. I'm not sure how to value aline after her nerfs but she seems a lot easier to deal with now so I'd try not to pick her.
Some of the best power cards are Goat Poultice, Goat Poultice, Shrine of Rebirth, Seduce, Stolen Plans, Strategem, and Summoning Portal. That reminds me, you usually want to draft exactly 1, maybe 2 purple onhold cards, Summoning Portal being the best one. Rite of Brood, Usury, Miracle, Malediction, Lackey (not with Doge!!), Synod, Mayhem, Fertility Offering, Ceremonial Dance, and Enchanted Urn are some other exciting cards to have.
Playing the deck well can be every bit as important as drafting it. Don't throw a huge minion into your opponent's seduce. If you're getting Empty Bank Syndrome, don't buy a cheap card and cause a chance to restock that cheap card back again. Don't buy a minion that's just going to get immediately killed if you can do something more useful first and get it later