you're asking very broad questions...
as someone new to competition BBQ, I'd suggest using the search feature to find many threads and also using the sticky threads at the top of this sub forum about Comp BBQ & Turn in Boxes.
From there, budget permitting you may also want to buy a book with insight on comp BBQ or attend a BBQ class catering to competition aspect
also consider finding a local competition in your area to attend and possibly lending a hand to a team
good luck