I think the same that soldier should at least receive half of normal xp for actions done in vehicle.
Currently xp is awarded for:
- Doing damage to enemy
- Killing enemy (I think this can vary, the more experienced the soldiers the less xp he receives for same kill than less experienced soldier?)
- Taking damage from direct fire (need actual HP drop, not the potential stopped by armor - so yes heavy in his armor receive less xp than other classes, at least from this source)
- Taking damage from constant sources like poison, acid, bleeding (more xp than from direct fire)
- Healing (using heal skill, not being healed) - so repair probably too
- Opening crates for the first time
- Reaching objective zones
- Removing mindfragger with mech arms
Most rewarding are kills, but taking or doing damage or even healing are not far behind in xp rewarding.
What more, I think that Technician should also receive some xp for his turrets kills. And maybe spotting enemy for the first time (if he is not spotted from the start) should be also awarded.
Skill points are awarded after leveling up. 50 points on each level. You have amount of xp required for next level on top of training screen.