1. Take a long drive on bike. And abuse it a little. If you are an experienced rider you will come to access about 80% of bikes condition
2. Start the engine and ask some one to put a foot over exhaust and lean forward to hear engine sound. Dont suffocate the bike for long time. 5,6 seconds will be enough to access the condition of bike (If you dont hear any unusual sounds)
3. Check its papers and check from nearest police station for any charges or any cases
4. Coming onto aesthetics, it depends on the amount you are paying. And check the market for correct bid
5. Check battery, tyre condition, brakes etc etc etc.