This is a compilation of the best commons and uncommons of each color. This is my opinion based on my study of the set as well as reading the opinions that have come out by pro players as well. Hopefully it can be helpful in what to look out for at your prerelease or in your drafts. Having a high level view of the good cards in the format can help you quickly narrow down on what color options are most viable during sealed. Take a look.
A great way to get your own feel for the cards is to start studying them through sealed and draft simulators.
Some of the main themes in white are allies, lifegain, and awaken cards. There's also some great removal and combat tricks as well to watch out for.
Blue looks to have some flying, awaken, and eldrazi scion themes. There's a bit of processor and ingest synergies that could work out as well.
Black has some lifegain, allies, and some sacrifice elements. It also seems to have a good amount of ingest creatures but only 2 processors, so look to other colors to get that going.
Red has some landfall, rally effects, and some nice combat tricks and removal. (My dream is to use Volcanic Upheaval on an awakened land. :D)
Green is big on ramp, landfall, and converge. There seems to be some good mana fixing with Sylvan Scrying and Natural Connection—which I didn't notice was an instant till today. It's hard to tell if 3+ color decks will be good but there's some good suppport from green. Giant Mantis will also be a great way to help you survive till the late game for some big drops.
In general the multicolor cards are great, so you'll always want to play them if your mana can swing it.
There's some sweet colorless high mana cost creatures that do some fun things. If you can live long enough to get to late game with a good eldrazi, then you'll be set. There's a few at uncommon that will do some serious damage, as well as some good utility cards.
Overall, I think there will be a lot of fun, complicated interactions that will make for a good limited environment. My plan for the prerelease is to to go for a Green/Black ramp and hope to get a Zulaport Cutthroat for some good value! Would also be fun to get a Blue/White awaken control deck going too. ;D
Have a good time at the prerelease!