1. Do previous sale research - Take a look at the current market prices by looking at completed sales on eBay. You can see up to 14 days of old information on eBay.
2. Pick the right season. Selling in October-February will yield a lower price than March-June. This is because most people list at the end of the season when demand is also the lowest. Plan out your sale.
3. Set a realistic price - If you set your price too high your wheels are just going to sit and you won't have any interest. If your price is reasonable people will at least take you seriously and make an offer.
4. List on eBay WITHOUT reserve - Resist the temptation to set a reserve. Setting a reserve on an auction is a big no-no. If you want to sell at a fix priced it is much better just to use eBay "buy it now" feature instead.
5. Describe properly - There are more than a few mis-described products for sale on message boards and eBay. Although you may pass your wheels on to buyers without issue, the ethics of this is surely wrong. Many times sellers simply don't know exactly what they have and fail to accurately describe their products. The result can be unsatisfied buyers asking for a full refund or partial refund. Do a little research ahead of time and be prepared to answer questions potential buyers might ask and you will save yourself a lot of headache.
6. Take good pictures - Take big, clear pictures for people to see. Tinypic.com is a great site for hosting large pictures on message boards and eBay has their own built ability to list pictures but it is up to you to take good pictures that show your product in a positive light.
7. Clean your wheels - It may seem obvious but clean your wheels before taking pictures. A clean wheel can easily garner 10-15% more than a pair of dirty wheels. Remove the cassette as well and show people what the freehub body looks like.
8. Add decals if they have been removed - Many buyers like the flashiness of stickers and they are definitely willing to pay more for Zipp wheels with stickers. If you removed yours then consider purchasing a cheap pair of new stickers on eBay for $10-12. It could easily net you and extra $50 per wheel.