Acquiring what you believe may be a valuable domain name is the easiest part of the equation.  Finding the right  buyer is much more difficult. Using auction sites and forums is perhaps the best way to find qualified buyers that are interested in your domain, and using auctions will take some of the stress away from establishing the value of a domain name yourself.
There’s an important distinction to make here between domain flipping and website flipping. The latter mainly refers to buying and selling full websites. By full websites, I mean websites that actually have content and more often than not have traffic and revenue. When buying and selling websites, the domain name matters less as the main value there is the content, traffic, revenue, history/reputation, sustainability and growth opportunities. The same can’t be said for domain names where you’re just selling “the name” and hence it’s all that really matters.