The hard work in the gym is a given, eating right is a given. The biggest mistake people make especially when prepping for a first show, is they don't plan, failing to plan is planning to fail after all. Seasoned competitive athletes already know that planning is the key..
Have the whole journey planned out, yes you may need to adjust things as you go, but at least it will all be documented. Documenting everything means you can use this plan everytime you compete. It’s like having the book of you, written by you about you, how you trained, how you ate, how much you drank, all the prep stuff, it’s all there in your book.