All of the above and groundwork groundwork and more groundwork. Get as much idea as you can from the owners what it has done/seen. Has it ha vaccinations before, dentist, cold or hot shod etc. never forget my mates 3yo arriving, she tied it up to the post, 30 seconds later it pulled back, panicked, snapped the twine and buggered off round the yard. Took us ages to catch him. It later transpired he had never been tied up before. Also has he been stabled, some youngsters live out 24/7 and when stabled for the first time they try to climb out. It's a tad unnerving when you see your new purchase with both front legs over the stable door! (also seen that happen!)