I know the fastest way to level renown is operations but sometimes you just can't get enough people to run ops at all hours of the day. What is the fastest way to level renown while playing solo? Heroics? Dailies? Flashpoints (not really solo but it's not an op).

My main is level 168. My renown is mostly through dailies by way of rep grinding

I highly recommend the heroics if you're doing purely solo leveling of renown - and only do the easy ones. There's a few lists out there for what are the 'easiest' for both factions, but doing those each day is a decent chunk. Be sure to use the Activity Finder thing to give you the Heroic Missions: <Planet> as that's even more renown from completing those alongside the heroics.

 

Do the bonus missions if they're easy/quick.

 

If you can, it's always good to earn renown when your light/dark alignment is winning. Not required, but adds some extra renown.

 

For extra sauce ontop, don't complete the Heroic Missions: <Planet> ones until the renown bonus day for Planetary Missions. Or especially on those days do all the heroics you can stand (some are cancer and I'd avoid like such).

And the CZ-198 dailies/weeklies. They're fairly quick and give a good-sized chunk of Renown. (Yavin's give more, but take longer because there are eight, and because they are more spread out.)

 

And always do Renowny stuff with the maximum +% buffs that you can get your hands on running.