Some experience for assistance.
Most senior collectors do not use CL or Ebay as a primary source, especially for rare games.
In priority order:
1) Private collectors - Individual connections (best option, keeps games with the "right" people)
2 ) Facebook - Closed collector groups (generally much more easy to get like minded people, and not just "flippers")
3 ) Private websites - Local collectors only, not forums (removes "flippers" entirely from the picture)
4 ) Dealer websites - Consignment sales (Keeps the "junk out of the trunk", but you will lose some profit)
5 ) PinSide (or other forums) - General collectors (More like minded individuals, but not necessarily knowledgable)
6 ) RGP - General collectors (Will get serious offers)
7 ) Mr Pinball - General collectors (can be a complete crapshoot now)
8 ) Ebay (or seller "stores") - General public (ad fees are wasteful)
9 ) CL - General public (by far the "worst" of all options, "flippers" are rampant and you will be wading through the cockroaches of society)
I start from the top of the list, if sales only, not for trades.
These are the most common, but there are more, dependent on needs.
If I had to calculate the highest % method of the 600+ games I have bought and sold, it would be #3 (private websites) at nearly 35%, followed by #1 (private collectors) at 20%. This is only because Facebook is a "new medium" that has really only come about in less than the past 10 years.
Only in my early days did I ever really buy anything from Ebay or CL, and only a handful overall. People are really rolling the dice with Ebay, because I nearly always politely ask for additional clear photos (as the ones on ads are crap), and the the response is usually resentful or why? This is especially true for bottom side of PFs or board sets.