What type of soil do you need to repot a bonsai tree?

I have a juniper bonsai, it's about four years old, I've had it about two. I've never repotted it or anything. I was just wondering how you go about doing this, what you need, and when to do it.|||Try John Innes No 2, it's what most retailers sell as bonsai compost and it works really well. February is about the time to repot, and as you may have to do some root prunning perhaps you should spend the winter reading up on the procedure. Better still ask at your local garden centre whether there is any one locally who could do it for you. Ask if you can watch so that next time you can do it yourself.|||use a bonsai pottng mix whichthey sell in small bags.