Use the 6 meter map on the DXMaps site to check for E skip. Whenever I see a lot of red lines on the 6 meter map, the guys in other areas of the country seem to be logging FM DX on the DXworld FM log in the corresponding areas.
For tropo, I've found the Hepburn maps useful. Usually when the Hepburn map says there is tropo in my area, I can hear the BC Canada stations a bit better. I never hear great DX, but I notice a difference in the stations I'm hearing.
The best way to FM DX is probably find a couple blank FM channels, program them into the radio's memory, and periodically check on them, aiming your antenna away from your local stations' transmitters to reduce QRM.