This is the first trick to learn for most jugglers (however my first trick was the reverse cascade).
The average person can learn to juggle cascade (to juggle 6 catches) in about 40 minutes.
But older people might take a little longer.
The fact is that everyone can juggle.

HOW TO START?
Grab just one ball and throw it to the other hand and back.
The peak of the pattern should be at eye level.

Then take two balls - one in each hand.
Throw first to the other hand and before You catch it throw the second one.

Attention! Both balls should be thrown at eye level.
The majority of people I have ever taught to juggle throw the first ball correctly but just hand the second ball to the other hand.That is wrong... dont't do it!)
Also take care to throw the second ball after the first one - not at the same time.

Change the hand with which You start to throw.

The time has come for three balls..
Start with two balls in Your dominant hand.
Throw three times - right, left, right (if the right hand is Your dominant hand) and catch all the balls.
Now You have two balls in Your another hand (that means left one).
So throw: left, right, left and catch.

Repeat it until You feel comfortable with it.
Then You can try to throw more and more times. And that's all. Congratulations, You've learned Your first trick!!! .

Note: You can also try to juggle two balls in one hand.
(You can use this ability in many other tricks like: columns or juggler's tennis.)