As I have mentioned before, when you offer to exchange links with someone, it can be useful if you offer a little something extra as well. One idea for that little something extra is to offer to put a thumbnail screenshot of their homepage next to their link. Thumbshots of sites are becoming increasingly more popular and it always makes a webmaster feel good when he or she sees a little screenshot of their work. A thumbshot is also a nice treat for your users as well, since it gives them a preview of the site.
You can also use a thumbshot as an enticement for a special listing. For example, the deal could be that the webmaster will place your link in a prime spot on the page (or on a prime page) in exchange for you listing their site with a thumbshot.
Thumbshots are usually approximately 120x90 pixels, but you can decide the best size for your page. There are many ways to create a screenshot of a site, and you probably have your own favorite way. If you are unsure how, check out this tip for nice, clear instructions and a list of software that helps as well.