Just the usual stuff for what I know..
Check fluids for color and smell, look for rust in the tank, leaks, cracks, weird welds, lights all working, registration (check numbers and dates for correct and current), check out the owner too (does it feel/sound right or like bs).. One thing I tend to do too is start the bike myself, preferably cold, ride it a little if possible, run it through all the gears (5?), let it sit idling for as long as you can (like several minutes) to see if it loads up and starts smoking... Oh, and run a little google search on it, 1984 honda xl200r, and read up on the lill' beast... Be informed.
Geez,, that was a lot of advise,, didn't think I had much to say.. lol
Current rides: DR650, CT90.
Riding whatever runs, wherever I want.