All good suggestions. A few tips though:
* Stay away from DP (at least when you're dealing with domains worth more than 20 bucks). While listing is free and there's indeed quite a bit of traffic, the price you get on DP is typically quite a few TIMES lower than you'd get elsewhere.
* Similarly, stay away from Flippa. Flippa is for sites, whereas Sedo, Afternic, NamePros, DNForum are for domains. That said, it IS possible to find a good buyer on Flippa, but it isn't likely to happen (Have tested. A lot.)
* Make sure you know the difference of end-user oriented marketplaces (Sedo, Afternic) and domainer-oriented marketplaces (NamePros, DNForum etc.). Sure, many domainers browse Sedo and similarly some end-users stumble upon NamePros every now and then but as a general rule - you should decide whether your domain has a lot of resell value (and therefore appeals to a domainer) or is it more beneficial to an end-user.
Good luck!