Buying and selling Domains is a tricky industry. You easily get addicted to it without really knowing what it's all about. Unfortunately I learnt a lot of the answers on here after losing 6k on useless domains. It is a constantly changing industry but the subject that keeps coming up is TRAFFIC. Organic type in Traffic. Those premium domains are long gone and you need to spend big bucks to acquire them on secondary markets such as Domain Auctions, Expired Domain Names, and Available Aftermarket Domain Names for Sale but if you keep up to date with future trends then you can spend less on hand registered names. You really need to think outside the box and spend a lot of your time reading industry leading blogs like business insider, network as much as you can and have a specific niche before jumping into other trends that you don't quite understand. There's so many ways of selling. Don't try and sell to other people who are trading domains aka domainers instead look for an enduser on Google by typing the name you own and if there's advertisers then you have yourself some leads or use tools such as Free Domain Appraisal and Domain Productivity Tools. A buyer can be convinced to buy if you have the numbers to prove how much that domain would be worth to them. Find out how much they spend on advertising per month then make comparisons with the number of direct type in traffic they get from your domain that you selling. If you can prove these numbers then it's easier to sell otherwise you better off holding on to it, maybe develop it the way Trump has developed his name until someone interested gets in touch. There's so many platforms where you can list the domain such as The world's leading domain marketplace , Park Domains - Afternic -DomainNameSales.com etc . Please NOTE I am not promoting any of these services but I have used them before and have had some success. Probably should have signed up for their affiliate programs but haven't had a chance before this question came up. There's so many other metrics involved so research as much as you can, don't spend a day without reading about the subject and go in at least knowing what you are doing. My two cents.
The second option requires a bit more time and effort than a 301 redirect. You could do a mini overhaul of the site and turn it into a microsite for your main domain. This option is good for exact-match domains for your targeted keyword, and there are other reasons for going the microsite route that Rand's highlighted in his post about root domains, subdomains, subfolders and microsites. This strategy also works better if the old domain has decent rankings for the keywords you're targeting.
Domain names comprising of a keyword have long since been regarded as a strong pointer when it comes to search engine ranking. This connection has been proven true over time. Nevertheless, keyword domains are still popular in the domain market. One reason for this is that keyword domains are seen by potential visitors as more relevant and are therefore taken more seriously. Catchy URLs containing strong search-volume keywords are therefore often monitored by potential customers over the years. It only makes sense to purchase an expired domain when the domain name coincides with the content, products, or services that you plan to offer with that address in the future.
Your course of action really depends on how much work and effort you can put into the expired domain. If you're barely able to maintain and optimize your current site, you probably want to just 301 redirect the old site (note: see my amended comment above about the link value not likely to be passed). If, however, you're more creative and have some time on your hands, you can try your hand at crafting a microsite. If you really know your stuff and are experienced at making money off various websites, you'd probably do well with the third option.
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.