[PerfAdv]

NismoJames, the link Dino_Scuderia suggested is a treasure trove of how-tos...

I don't have a lot of experience and my cars don't turn out anywhere as nice as the ones at this contest and some of the other posters right here are far more knowledgeable than me but here's what I do.

For the mold lines, I've had some success by prepping the car for painting then first spraying with primer. Tamiya has what they call Surface Primer, I get it in Gray. Then sand the entire surface lightly. The high spots and mold lines will appear and you can then concentrate on them until smooth.

One of the mistakes I use to make was being rushed, which caused small imperfections in each step, adding up to a less then stellar job at the end. Be methodical and patient, always let primer/paint/clear-coats dry completely before sanding/wet sanding/polishing.

Although it's nice to pay a lot of attention to a complex model, I've found the most difficult part is the body painting. Complete more simple kits rather than a few complex ones and your expertise will develop quicker...