Describe your own site in a few words, and invite the site owner to visit and make any suggestions or comments. It is good to show respect and this builds rapport. Finally, don't forget to follow up and check the link is on the site as promised. A gentle nudge email is appropriate if the link isn't reciprocated. Also, remeber to check your links often.
People hate being sent off to an error message.
Keep this up religiously. It is a great technique and will serve you greatly, so don't get lazy. It is the best time you'll spend marketing online. It might be worthwhile to add a message on one of your pages offering a link, or even a gift or incentive if they do. How To Get Hit On.