DGB and BJCP. And I almost always follow the same hop schedule regardless of style unless it requires no aroma. What helps is having an example. Preferably more than one. So drink up people.
+1 to DGB and BJCP Style Guidelines. Designing Great Beers is a GREAT book with a great approach. You can create a recipe for a style and be able to see what ingredients (and % of each ingredient) are common in that style. It really helped me get a handle on things across a big range of styles. Learning the attributes of each malt, hop, and yeast will help dial in a recipe, and I learned by changing only one ingredient or variable at a time. Take really clear,thorough, legible notes (including water chemistry)that you can reference. Be sure to add detailed tasting notes - I might not make a style that I brewed last year for another year or two, depending on the style. What was great, good, mediocre, or sh#$$y about it, and what would I change next time? Easiest to assess while you're drinking it than having to try to remember. Good luck.