Ways to earn experience-points
Here's an expanded list, although I make no promises about its completeness:
Completing bonus objectives in a quest.
Helping a member in your group complete a bonus objective in their quest.
Yes, that means that more than one person in the group is doing the same quest, you get the XP for your bonus objective plus the bonus XP for helping your friend for each member in the party that had the quest and bonus objective.
Exploring new areas. Each time you fill in a new part of a world's map you get a spot of XP, plus another spot when you've discovered all areas on a given map.
Reading 'lore objects'. They vary from blatantly obvious to incredibly easy to miss.
Participating in PVP warzones. I'm not privy to the exact formula by which it calculates the reward, but you gain XP, "valor" and cash even if you're not on the winning team.
Things that don't give XP:
- crewskills and crafting. Their expertise level is entirely independent from your level progression.
As to your last point, SW:TOR does have a 'resting' bonus; rest areas are cantinas on planets, the main space station of your side's fleet and the interior of your ship (earned after completing your class story arc on your side's capital planet). Rested XP accrues while you're in a resting area whether you're logged on or not at a rate depending on your level. So far I haven't seen or heard of an upper bound on the amount of earnable resting XP.
Finally, after completing the first "chapter" of your class story arc (mid-thirties) on the first character you get that far, you get the not-optional option of choosing a 'legacy name' that can then get displayed as part of your character title and is shared among all alts on that server regardless of side, and all your alts on that server will start to accrue "legacy XP" that's again shared. It currently doesn't seem to do anything, but it's there for Bioware to attach stuff to later on I guess...
Space missions award a non-trivial amount of experience as well. When you unlock each "tier" (first should be available when you get your ship, and consists of three missions. Second opens at level 20), you'll get a set of quests from the ship computer, one for each mission in that tier. These award 8-10k each, plus the experience for the mission itself.
Once you've completed the single missions, you'll get the repeatable "campaign" missions, which usually encompass the whole "tier" (exception for the first tier, which is broken in two, a single one for the escort, then a double one for the other two). These are dailies that award 8-10k.
Completing the first "tier" of missions, as well as the campaigns for the first time, has consistently gained my characters just over a level. That's doing them as soon as the ship becomes available, usually around level 15-16.
In the space missions themselves, there are optional objectives to complete, which also award experience.
There are hidden objectives as well. For example, in the first-tier "Cartel Listening Post", there's a heavily-shielded attackable point on the bottom of the space station. Destroying this (use missiles every chance you have, it takes quite a few, at least at level 1 upgrades) will gain you an additional 2.5k xp/credits. This appears to be a daily as well. Destroying it in subsequent runs gains you 500xp flat out, no bonus.
For the first tier, running that particular mission (without the associated quest) awards ~330 credits and ~1900xp each time, in addition to what's acquired in the mission itself. You can easily reach ~4k per run.
These don't appear to take Rested into account, however.
- Quests/Flashpoints (and bonus stages)
- Bonus parts of quests
- Area quests
- Companion storylines
- Space combat
- PvP
- Exploration
- Finding datacrons
- Bonus rested experience (when you log off at a cantina, your ship, or at the fleet)
- Killing mobs
- Talking to each of the crew skill trainers the first time (usually when you get to the fleet)