Not certain you can bone up for aptitude tests. Maybe just do a few mathematical puzzles, brush up on your reasoning skills, work on your fine motor skills/hand eye coordination. Best would probably be to get a good night's sleep the evening before so you're ready for things and have a good breakfast so your blood sugar doesn't crash. Avoid anything that takes a lot of energy to digest as it could make you dozy. Relax and enjoy it rather than go in there on edge and spring loaded to the panic position. Most companies also check you out to see if you have the personality to fit in on the flight deck so just act as you would normally do.
Good luck....