A basic check would include weighing them. Keeping a record of weight is a good way of monitoring health as often unexplained weightloss is the first sign of a problem.
Check eyes- should be bright, free from gunk and not 'watery'
Check inside ears for any signs of a build up of debris or an offensive smell
Check around mouth for dampness/excessive staining. Feel along jawline for any lumps. You should be able to check Incisor teeth but you wont be able to check the molars.
Check nose for any discharge
Check coat for signs of mites (white dandruff) or fleas
Check bum and 'bits' which should be clean and dry
Check scent glands for excessive build up of waxy secrertions
Check length of nails
Check hocks
Feel all over for any lumps or bumps, scabs or injuries