As far as the elements go Pokemondb.com is your friend. I look up almost everything on there before a battle and pick my 'mon attack squad accordingly. They have 'mons listed with a chart of "does half damage" "does x2 damage" and sometimes "does x4 damage" and for the most part it's accurate!

For the most part meaning the same mons don't always work as effectively against the same mons. I got really lucky with Flareons against a Nidoking once, tried the same tactic against another Nidoking and had much better luck with Vaporeons. Go figure.