5. Quality of witness testimony and sightings/encounters.
5.a. High witness credibilty when: Pilot, Astronaut, Scientist, military or other professional, did not believe ETH prior to sighting/encounter, have no motive to lie, telling about sighting is detrimental to witness.
5.b. Multiple witnesses see/experience same ET event.
5.c. Photo + Video evidence (Esp. when in combination with any of above or below points)
5.d. Pilot intercept. (Esp. when in combination with any of above or below points)
5.e. Radar contact (Esp. when multiple radars show same object + when in combination with any of above or below points)
5.f. Some abduction encounters seem credible.
5.g. Testimony of people I personally trust absolutely.
5.h. Some Sightings/encounters include seeing/interaction with (usually small) humanoid occupants of the craft. This is one of the most compelling arguments for ETH as this can hardly be anything other than ETH (Expect perhaps time travellers or interdimensional travellers).
6. The posibility that alien implants exist.
Note: Sometimes we have multiples of the above points occuring simultaneously - obviously this makes the case for ETH much stronger than any single point.
those make for a good scoring system Pax