I did this last month, snagged a great domain that no one else found and got it for $69 because I waited until the last moment to place my pre-bid. Flipped it within a week for a little over $1,000. And probably could have gotten more if I sat back and waited 6-12 months, but a bird in the hand… (plus I like to keep turning over inventory and maintaining cash flow).
One of the best ways to obtain a valuable domain that is already search engine optimized is to purchase existing domains via auction sites.  This strategy can be beneficial mainly in two ways.  Firstly, any domain that has already been purchased was probably already researched for potential benefits.  Secondly and more importantly, the second benefit is that many recently expired domains still retain some of the search engine optimization attributes that were built up by the previous owner. For example, a recently expired domain name may still have active backlinks on the web, and the page rank of the domain could still be high, giving the purchaser instant SEO gratification with minimal effort.
Check backlink profile: If you’re not familiar with what backlinks are, they’re basically any public website that “links” to the domain in question. Since there are numerous shady tactics in the SEO world, expired domains’ backlink profiles should be examined carefully. Check if too many links are coming from the same domain or if links have weird anchor texts/use foreign languages. You can use a tool such as ahrefs for these purposes.

I have some pot related ones I've purchased recently that deal with the manufacturing of hemp like hempmfr.com, hempmoulding.com, hemp-textiles.com, hempecofuel.com etc.  Some of the older domains I've been sitting on are ones like internetpot.com, califunk.com, cafunk.com, caedibles.com, 1tokewonder.com, govherb.com, grasspeddlers.com, pot-megastore.com, usgov420.com etc.  Another interesting recent on I've purchased is Dogparkdates.com and dogpark-dating.com. Do any of these seem valuable in your eyes?
It is much harder to sell names no one has heard of. Short names have the highest value — they are rare, easy to sell and bring substantial profit. Basic and common domain names, which can be relatable, or arouse interest in the market are the best. General names sell thick and fast and also bring considerably higher profit.  Names that are easy to spell will attract buyers, and provide good opportunity to make a decent profit. If you know you have a good domain in your hands, then you are likely to make good profit by selling it.
Your domain name registrar may provide you with a free one-page Website tool, which you can use to create a “this domain is for sale” landing page. Alternatively, you can create a single page (perhaps a hidden page hanging off one of your existing websites) that indicates that your domain names are for sale. You can then forward all of your domain names that are for sale to that one page.
The domain name industry is quite similar to the real estate industry in a lot of aspects. There are end users, brokers, consultants and domain flippers or “domainers”. Domain flipping works similarly to buying a house, renovating it (or even sometimes just sitting on it) and then selling it again at a higher price point. The gist of it is: you’re purchasing a domain name and betting it’s worth (or will be worth) more than you paid for it. If you’re right, you get a nice paycheck and move on. Those who make a living out of this just rinse, repeat, and scale.