Go to the IMAC website and take a gander at the rules: Mini-IAC.com

The first thing is that for Basic Class a scale airplane is not required. Personally I would love to see someone show up and fly a CE though, major cool factor IMO. While on the IMAC site download and print out a copy of the basic sequence. Most guys are capable of "Flying" every manuver on the sequence. Notice what I did there? There is a huge difference between flying a Cuban eight and "performing" a cuban eight so that it scores well. The first thing you will need to do is set up your CE so that it will fly the sequence easily. For most guys this means reducing the rates, fine tuning the CG, get the engine thrust set correctly and making sure it is 100% reliable. Then comes the practice. For new aerobatics pilots, I suggest just going out and practice strait lines with turn around manuvers at each end. Almost everyone then realizes just how difficult that is. The goal is to position the airplane about 150' from the dead line and keep it there, with wings level while doing 1/2 cubans, humpty bumps or sharks tooth turn arounds. Practice this until you can keep the box depth, then start in on the sequence. Keep a relitive slow pace between manuvers, rushing the judges always ends up in poor scores.