Get the signs from your coach while you are standing on the base. This is more critical than at any other base because your back is toward the pitcher. Once you have received the signs, take your lead. The biggest difference in taking your primary lead from third base rather than from first base is your need to stay clear in foul territory. You don't want any question if you are hit by a batted ball, you are in foul territory. Another difference is the pitcher may be pitching from the stretch or from the windup position. It's easier to be more aggressive in your secondary lead if the pitcher is pitching from the windup; regardless, the goal of the secondary lead is to get your momentum moving toward home plate to maximize your jump on a batted ball. Make sure you don't move into fair territory when taking your secondary lead. Strive to have your right foot hit the ground as the ball is entering the hitting zone. Always watch the ball all the way from the pitchers hand to the plate. The trajectory of the pitch will give you a good indication of what might happen.
Another important point when taking your secondary lead is to make sure you keep your hips and shoulders square to the field so you can easily continue towards home or get back to third quickly if necessary. A good catcher who sees the shoulders squared towards him will make a throw to third. This position therefore will not only cause the runner to be slower getting back to third, but will encourage more throws from the catcher.
Once the ball has entered the hitting zone, it will either be hit, fouled off, get by the catcher, or be caught by the catcher. If the catcher catches the ball, have your weight on your right side. Push off your right foot and crossover back towards third base and fair territory. Even though you took your lead in foul territory, you want to return to the bag in fair territory. The reason is if the catcher is going to attempt to pick you off, he has to throw the ball accurately to the inside of the bag. This makes it more difficult for the third baseman to make a quick tag and it may result in a bad throw that either hits you or ends up in left field. Whatever the end result, you have placed more pressure on the catcher by returning in fair territory.
Any ball hit in the air, you should start back towards third base. The general rule of freezing on a line drive doesn't apply at third. If it's a line drive that gets through the infield, you'll score easily even if you start back towards third. If it's a fly ball, then you need to return to third to tag up.
Knowing when to run home on a ground ball with 0 or 1 outs is very difficult. The depth of the shortstop and second baseman will let you know if they are willing to give up a run for the out or not. If they are deep you should be able to score on any ground ball hit to them. Most third base coaches will let you know what to do depending on the situation, he may tell you to hold if it's hit to the pitcher or third baseman and run if it's hit anywhere else. Even if those instructions are given, you must still read the play and determine what you will do.