[prog] balancing a binary tree

[ed orphan]

Can anyone direct me to a tutorial on how
to balance a binary tree?
I've got plenty of information on how to
build a binary tree, but from what I've read,
after a while the tree becomes unbalanced
due to insertions and deletions. As a result,
the tree's efficiency goes way down.
Not much purpose in using a tree if it
self-destructs efficency-wise and I can't
repair it.
I'm writting in GNU C using Slackware Linux.
Any information would be most welcome.