Things I looked for on my bike,
Nice chain(well maintained)make sure the links aren't dry and lube on it isn't old . Check for appropriate chain slack.
Check sprocket for worn teeth.
Look for scratches/cracks on/under fairings, under cowl.
Underneath bike for signs of cracks from pothole damage, scrapes.
Check forks for leaks-->low Kms/ newer bike with leaks may indicate possible stunting
Check oil window to see color of the oil. Make sure it doesn't look dirty and old.
Look for vin number to match.
Look for one with frame sliders (some bikes need modification to fit sliders)
And stands (that way you know it was stored properly winter time/no flat spots on tires)
Check tires for wear pattern to signify owners riding patterns, see if outside line is worn (rider goes mad twisty and guns it more) or inside line (rider is more conservative) .
Make sure all lights work, make sure there are no scrapes on exhaust to signify a slide and fairing change.
Check handle bar-> wheel alignment(visual)
Check handle bar ends for scrapes,drops , lever ends for scuffs and to make sure they are straight.
Me personally I picked FI. No carb diet here.
Start up the bike, listen for any strange knocking noises. Or violent ticking noises, except for the cct(cam chain tensioner) .
If the owner starts it up, see if they throttle before it warms up (that way you know they do that usually) responsible motorcyclists warm up their motorcycles before riding. Gasing with no load is not good for the internals(check out different bike).
After checking tire pressure and horn, giddy up.
Check brakes on riding , feel for rotor pulse if any.
Check clutch while shifting, make sure bike goes into
All gears smoothly.
Make sure bike gets hot enough for fan to come on.
I carry nylon gloves and a flashlight when I go to check out a bike.
Check for leaks by seal area(some people clean area before viewings, so look in corners/wipe behind hard to reach places for sludge marks/gunk buildup)
A clean and well maintained bike is the signifying point of the owners love.
Look for any cobwebs which may signify low use.
Curb rash on rims and if rims are straight.
Depending on what you find, you may be able to haggle for lower price in your favor.
Most importantly, Never buy based just on excitement!
Edited for additions and clarifications.