OK, I have all the sub assemblies basically made for a Great Lakes Trainer.  It is a 1"-1' Sterling kit.  I would like to use this in "Fun Scale". ("first timer"!)

What are the next steps I need to take before I assemble it all and paint it up?

Thanks!
Bill

Everything Clancy said is right, they judge your model based on the documentation. In other words do not prove to the static judge that your airplane is wrong. One mistake made over the years is to put your AMA number in place of the scale documentation. The scale model must match the documentation down to the numbers. Put your AMA number on the inside.

Then practice at the flying field and know what scale options you plan to pick out. For a single engine biplane you will probably use the following options

45 degree flight
Touch
Go
Overshoot (google the FAI judging guide for what this looks like)
Taxi
Throttle control

Touch and go counts as two options so i list touch on one line and go on the next

To get full points for throttle control you need to be able to shut down the motor from the handle on command

Some folks at the nats did not good ground handling with the models. Make sure you can idle the motor down to idle and come to a complete stop, then throttle up for takeoff or taxi

Also make sure everything works when you get to the field

Good luck
Fred cronenwett

Actually you could use the plane for either Fun or Sport scale.  Often-times, Sport is sparsely attended and actually easier to win than Fun.   

For Fun you only 10 static points.  A halfway decent plane will get 7 points and you could really knock yourself out and get 9.  But you really need to max out the 100 flying points, so don't degrade the flyablity by going overboard on static.

In Sport with the 100/100 ratio, you might need to put more work into static even if it hinders the flyability.

Two key elements either way:  Throttle operation and the Landing Gear. 
You need to be able to dead-stop the model without killing the engine, then kill the engine on command.
Takeoff, touch & go, landing, and taxi lap.  Five ways a landing gear will make or break you.