[nemonemodory]

Well usually you would pull it out of the pot, and cut some roots. I'd trim down the really long ones, and any that are circling around the sides of the pot.
Just don't cut too much off.

[Joe Pelonio]

How in the world do you check and prune the roots of a juniper.
 

First look at the hole on the bottom of the pot, if roots are visible or coming out the bottom it needs root pruning.

If you gently try to pry the tree soil, roots and all out of the pot you will see if it's getting rootbound. In otherwords if there are roots winding around the inside of the pot, and more roots than soil visible at the bottom.

Typically every other Spring, your bonsai will need to have it's roots pruned.
You remove it from the pot, take the soil off of the outer roots, and trim off no more than 1/3 of the roots, all the way around. Return the plant to it's pot, using a mixture of household potting soil with 1/3 part sand added, to replace the lost soil. Some people will soak it in a solution of vitamin b-1 transplant mix and mist with water a couple of times a day for a week or two.


Here's an article another member recommended a while back that might help.
http://www.bonsaikc....g_technique.htm

[nemonemodory]

How many times do you have to prune your roots.

It depends on how fast your tree grows. Joe said every other Spring...

[nemonemodory]

I am new so, do you know of any good books on bonsias?

I know of one, it's called The Bonsai Workshop, by Herb Gustafson.