You've received good advice so far...
IMO, the most important thing is to learn to read the Elephants' body language as others have explained, and to respect the amount of space they want.
Just like you and I have a bubble of "personal space" around us, so do elephants (Theirs is just a lot bigger then ours!). The ones in the North tend to have bigger "bubbles" than the ones in the South. They will very clearly show you when you are getting to close, and as long as you can understand their signals and respect them, you're fine.
Enjoy your trip!
