I would recommend that you regularly check to ensure those you have traded links with are keeping up their end of the bargain. You may be surprised at what you find. Today for example I was checking the reciprocal links of a client’s site and found that 100% of the links we had carefully accepted over the last couple of years had stopped linking back. Every last one!
The links we were providing to these cheaters were all good links on a PR3 page – which was way better than we were getting in return in the first place. There was no reason for these sites to remove their link back. I guess some people just like to take advantage of others.
So, even if you carefully check out potential link exchanges (as outlined in other posts here) to ensure that you are getting a fair trade – you need to keep checking to make sure you are still getting value and are not being taken advantage of!