A good idea is to choose two or so types, and build your deck around those. For instance, if you get a number of good Grass and Water types, you should use those in your decks. Also, for each set, there is usually a thread on here that discusses the good cards of a certain's sets Pre-release. The SV happens to be on the first page of this forum, so if you're going to an SV one, you might want to look at that thread for some ideas of good Pokes to use in the PR.
As for Trainers, use ANY Trainers you pull. Nearly all Trainers you pull will be useful at some point, even cards like Potion and Energy Search. If you pull any Special Energy, it is probably a good idea to run those as well, unless you have SP Energy but no Pokemon-SP in your deck. In general, about 16 to 22 slots of your deck will be Energy, around 14 to 18 slots will be Pokemon, and around 2 to 6 slots will be Trainers.
Colorless Pokemon are also decent in the Pre-release, seeing as they can use any energy type. If you get a 2-2 line of a decent Stage 1 in your packs, you should build your deck around that, as a 2-2 line is pretty good in a PR.