[smiling]

Basically,

you don't exchange links with any page with a white bar.

Don't exchange links with any site that has a huge link directory

Always view the source code to make sure there's no monkey business

Always check the robots.txt to make sure there's no monkey business

Always check the backlinks of any sites they are linking to to make sure they show up as a backlink

Never trade links with anyone who approaches you for links

Always trade links with those that you approach