Make sure the bits that open and close do so properly. Ie, any hatches appear to seal well enough, zippers work well. Make sure you put the tent up and have a look for any tears etc. you are likely to see rub marks if it has been used, so don't stress about those unless excessive. Lift the mattress and check there is no damage on the wooden bed base. Putting it up also checks that all spreaders etc are fine. Give it a sniff for mould.
Check the tub and draw bar for signs of dent repairs. If it has been used, any paint will not look like new, so if it has been repainted see if you can find out why.
Start planning your first trip away in it. Enjoy!
