Straight Surface.
Make sure your surface beneath the ceiling tile (available at lowes/homepot...get 2 while your there) is straight and ridgid. NOT THE TOP OF A CARD TABLE. They sag...i found out the hard way on my first kit many years ago....not much...but enough. I lay mine on one of those ponderosa pine things also available at lowes.
They will love you when you pull them all out to look for the straightest one. And then they will gasp when you actually put them back.
Remember, the investment into kit building is like jumping into the hobby at first. The initial expenditure on tools (like radio gear) will eventually be spread across many models in many years...skimp on the tools for the first one to make sure you like it. Then for your second or if your sure you will like building buy good tools and more importantly "the right tools for the jobs" and you will love them.\
DONT Spoil yourself with a laser kit up front....wait 4-5 kits down the road when your tired of shaping and sanding.
Nick