what to do when buying a ped (check frame etc)

Ok i hope someone on here really knows their stuff
cause a sticky of what to do when buying a used ped etc should be done

Ok thing is when buying a used ped it could of been in a crash or anything and just had panels changed etc

so the most important thing to me is how to check a bent frame
or is this called wheel alignment? (or is that a totally different thing?)

i ask this cause i just bought a bw,s and it feels very very wrong when i ride is exspecially when i take corners (which makes me think something is wrong with frame or wheels)

also how do i check forks are 100% ok

deff a list should be done on how to check certain things

cause no point in a running engine if he rest is messed up

some help wold be appreciated cause im thinking to return the bws
but this info would be great for anybody plus me in future
so help guys