This is the first trick I learnt how to do when I learnt how to pass. It's not the most amazing trick in the world, but it is easy to get the general idea of how it works.
The catches for doubles are slightly different to normal catches, they tend to be tilted back slightly, but with practice you will soon get them right.
STEP 1 : Do a standard passing pattern.
STEP 2 : Throw your club across the pattern and higher than normal with a double spin.
STEP 3 : (If done correctly then it should fit in the pattern.) The club that you throw as a double to your partner should come straight back to you as a normal throw or a double(see Tennis.)
Variations
Left Hand Doubles
If you want to do a left handed double then follow the steps above but throw the club that comes from your partner as soon as you have got it with your left hand. This in theory should fit in to the pattern.
Tennis
You can keep throwing one double, the same club, between you.
Continues
You can also throw every club you receive as a double.
Left, Right continues
It is possible to throw your right double then your left double and so on. But this is one of the more advanced tricks that you can do with doubles.