How to Juggle three objects.

Step 1: Start with only one object and both hands in front of you. Throw the object up-and-across your field of vision to the opposite hand. You should look at where the object peaks in the air and be able to adjust your catch based on that peak.

Step 2: Repeat step one... about 200-1000 more times. Right-to-left, left-to-right. If you were juggling a glowing orb at night and took a long exposure shot your pattern should eventually look like the infinity symbol. You should be able to easily toss the object from hand-to-hand without having to move your hands around too much.

Infinity pattern associated with juggling.

Step 3: Now that you have practiced throwing one object from hand-to-hand and you can do it comfortably you may be ready for three. (You can skip two, congratulations!) The first thing you should do is hold two in your dominant hand and one in the other. Throw with your dominant hand first, just like you've been doing.

Step 4: OK, your brain is probably panicking a little bit. Just catch that object in your other hand. Now you have two in your non dominant hand and one in your dominant hand. Throw it back.

Step 5: Repeat step 4 a few times, then once you are comfortable with that feeling try throwing the object from your non dominant hand before the first object lands. If you catch both try throwing the third.

Step 6: You should be comfortable throwing and catching out of both hands now. Your juggling pattern will look like this.
Throw Right
Throw Left
Catch Left
Throw Right
Catch Right
Throw Left
Catch Left
Throw Right
Catch Right
Catch Left

Now keep it going! Good Luck!