Pit stop: we don't use pit speed limiters so configure your pit stop well ahead. You need "Pit limiter", "Confirm", "Ignition" and "Starter" buttons in easy to access location( for ex, pit limiter is in my wheel, confirm and all other pit functions are in separate keypad that i can access without looking).
Going to pits you go full speed and switch pit limiter off when it's auto engaged, press "confirm" to confirm your pit actions. When you refuel, your engine switch off. You can engage "Ignition" while it's refueling and start your motor when changing tires ( i do both when changing tires). This way you win 1-2s. Don't use autopit, it is not supported by all modded tracks (And you lose that 1-2s when your car is started, after it's wheels have changed and it's dropped to the ground)
While in pits, all vehicles are in "non-collision" or "ghost" mode (respective to each other, you can still collide with buildings etc) so you can drive thru vehicles if someone is in your way. If you're pit box is close to pit entry and you need to brake before the line, please notify it to others to avoid collisions.
Pitting is complex but i feel that it's complexity is essential part of the race today. A lot can happen, you can mess up before pits selecting the preset (oh yeah, make presets before race so you don't have to start doing math while racing..), overshoot your pit box, leave pit limiter on for too long, panic and forget to press "Confirm" etc. It can be VERY nervous experience and you need to start thinking about it early. Call pit crew at back straights ( in Interlagos at least in the last tight corner.) Pit crew takes 10 seconds or so to be ready. Choose your pit preset well ahead (i glance at it few laps before pits, just to check everythings ok, then drive until pit stop is imminent and make my pit call early. I get full confidence and can concentrate on pressing buttons). Interlagos has nice long turns at the end so you can go thru all actions needed with plenty of time. While still of course racing safe and fast.
On tracks where pits are close to tight sections at the end, it's more important to choose where in the track to do what action. For ex, i wouldn't go selecting pit presets while going thru Beckets or Eau Rouge.
Good luck
Practice practice practice..