Well here are a few tips based on some grueling experiences I went through licensing my tracks, hope they help.
To start, I use https://soundrop.com/ as my distro service; it's not as fast or as friendly as it used to be unfortunately (live chat disappeared in favor of a slow ticketing service, for example), but I still get monthly play reports and it's great about regularly adding (and including your materials) on new platforms as they become available.
As to licensing the music, here's the kicker: they require proof of a U.S. release of the original track. That means before you even want to try licensing something, see if the source soundtrack album exists on Apple Music or Amazon (the two they put the most stock in). (That part also used to be easier, but the restrictions changed a few years ago.)
If you can hunt down an ISRC (album) or UPC code (track), even better! Musicbrainz.org is a great resource for that. For example: https://musicbrainz.org/search?query=Grim+Fandango&type=release&limit=25&method=indexed
Each track you want to license gives you a spot to include a write-up, so come with everything - track title from the game, composer, soundtrack title, official album release links, codes... you'll be in good shape.
If the track you're licensing has multiple source tunes, be prepared to include both in the description.
Sadly there's a ton of material I couldn't license after maaaaany attempts, because even though I could prove US game release, note the production company and show the Wikipedia article, there was no official album. Doom 2, for example. I found some album records online but if you look closely they say "bootleg" as the "status" and that doesn't work well. Not official enough.
Anyways I hope that helps, take care!