Oh, and the BIGGEST advice, don't view it:

In the dark - you'll not be able to see all the horrors
In the wet - make shat paint look mint
Alone - makes it hard to look while the seller is ratttling on and you end up getting carried away, a mate will be cooler, keep the seller chatting and stop you buying a lemon.

If you ignore the above, you may wake up in the morning, go outside and think WTF have I bought.