I would do some research on what federation you would like to compete in. The NPC is most widely know, you can find information on shows at npcnewsonline. Contests are usually around the same time year to year. Next I would see what division you think you might fit in best: bikini, figure, fitness or bodybuilding. What's the difference? Bodybuilding: most muscular of the group, hit mandatory poses in addition to quarter turns. Figure & fitness: not as muscular as bodybuilding but some degree of muscularity. Both do quarter turns but fitness does a floor routine and both wear a two piece suit specific to figure/fitness. Bikini is the newest category, less muscle of all the divisions. Can wear any bikini as long as it's not a thong. Bikini also doesn't do quarter turns they just do a front and back pose. You can find more information on the NPC website.
Some things to think about:
-select a contest
-select a division
-get your diet and training lined out for however long you think it will take...then add about 3 more weeks to that!
-start shopping for you suit
-order clear heels (need to practice in these)
-practice posing and walking, this is a lot harder than people think. Best option is to have someone who has done it help you.
-select a tanning product made for competitions (Dream Tan, Pro-Tan or Jan Tana)
-get your NPC card
- practice stage make-up
-Make travel arrangements
This would be a rough starting point. Hope it helped some.