Avoid freeway if possible; travel to and from the airport on surface streets, particularly during peak hours. Get to know La Cienega, Sepulveda, and Lincoln. (Added bonus for many, the In N Out on Sepulveda!)

Re: parking: sometimes cheaper to stay a night at airport hotel and leave car there for long trips, taking shuttle to/from hotel.

During peak arrival/departure times, T1 (in particular, also TBIT) can cause major traffic - so go to the opposite (downstairs when upstairs busy and vice versa) and take the escalators/elevators.

You can indeed walk from T1 to T6/7 across the tops of the interior parking lots, and this is sometimes faster (if you are rushed) than waiting for shuttles.