If there are less than 2 outs, lead off then tag up and run if the ball is caught and you can make it to the next base. With two outs, run like mad!

go two steps off the base and if they catch it go back

Go back to the bag and tag up because even if they catch it its still a run but dont get thrown out!!!

it depends on situations. if the ball is caught you go back but it depends on if it is a force out or not

Another important thing is how far you lead off. If the pop up is hit near you, lead off less than you would if it were hit far away from you.