Medical is pretty basic, you don't really have to prepare for anything just be calm and follow instructions.
Yeah basically as Sarah said... don't listen to loud music as the hearing test is quite hard, some beeps are extremely quiet.
Basically this is the step by step things i did when i was there.
1. Fill out a form about previous illness and known diseases/allergies
2. Height + Weight measured
3. Lung capacity checked (had to blow hard into a tube)
4. Blood pressure taken
5. Urine sample (had to pee on a little stick)
6. Hearing test consisting of wearing headphones and the guy playing sounds through his laptop gradually changing the pitch/frequency and going from right to left ear
7. Stripping to underwear and had me doing 5 push ups then squatting and moving forward in a squat to show flexibility
8. Eyesight test - reading letters on a wall from far back
9. Colour blindness test - just reading numbers in a booklet with different colours in different coloured backgrounds
10. Listened to my heartbeat
This should be the basic drill just to give you a vague idea of what it will be like, not promising it will be the exact same!
Goodluck with your medical & the rest of your application process!
Matt