Generally speaking, on corner entry and mid-corner, you're always better to be inside. There's usually more grip there, you're less likely to make a mistake down there because you're used to driving on the inside and, in the event of contact, it's not usually catastrophic. At a start for example, I'd always give up position to get to the inside, whenever possible. If I can enter a corner 6th but on the outside or 8th on the inside, it'll be 8th most of the time, especially in tighter corners. Just being on the inside will often gain you a couple of spots as guys are forced off into the gravel. May not be much of an issue with the rolling starts though but it certainly applies to pack racing.
Also generally speaking, the motus operendi of most of the weaker drivers online, is to brake too late, get the car out of shape, and lose exit speed. Exit speed and getting on the throttle early is the key to being fast online and in real life. You can usually figure out tendencies in a couple of corners and then plan for an over/under move. Pressure him almost up to the braking point, take a slightly wider and slower entry than normal, rotate the car towards a slightly later apex to get on the throttle as early as possible, then complete your pass on the straight. The late apex may not even be necessary if he gets enough out of shape.
Capitalizing on mistakes and carnage is important too. If you see a couple of guys ahead of you bumping and grinding, leave a little space to stay out trouble, but be ready to pounce when the inevitable contact occurs.
Practice is important. Once I've figured out a track, I start practicing overtaking on my own. I take corners on the outside to see what speed I can carry. I dive low on the inside under hard braking to see what happens. If you don't practice this you won't be ready for it when the race starts. Endlessly hotlapping on the racing line isn't the best use of your practice time.
