Ok here are my steps. 1. Decide what to build, factory stock, custom, streetrod, etc. then research that build so you have reference materials. 2. Get the kit and locate all necessary items needed and decide your color and theme. I build everything in sub assemblies then bring everything together in the end. I then make sure i have enough time to finish my project. I wash all my parts as i build each section then allow them to dry. I test fit the body to everything from bare plastic to primer to final paint. Theres nothing worse than having a pristine body in paint and nothing fits.
I do the body first, then engine and chassis next. I do the interior. Then assemble everything taking my time. I have found investing in a tamiya rotating paint stand is good because it allows you work on the body and rotate it without touching it. Also invest in good polishing cloths, good polishes and a good polishing kit. The sanding pads work best. Also get a good pair of cotton gloves so you don't mar the finish.
Start out building what your comfortable with and as you get more experience try new things like photoetch custom paints and engine detailing items. Use good quality foil for your trim. And don't be afraid to try new ideas. I always have a copy of the flyer for the show with the categories so i know what to build for what category.
Last thing is i bought a set of plastic storage drawers from fred meyers so i can put each project in its own drawer so that parts and assemblies don't get damaged or lost while you are doing your project.