How deep does the trench need to be for new electrical work in a conduit?

I am rebuilding my garage and the existing wire from the power pole to the weatherhead on my house hangs too low for the planned roof height. So, my Public Utility will disconnect and reconnect my Overhead service to the back of my garage when the garage is finished. I'm hoping and planning to put the wire or wires from the new connection on the back of the garage in a buried conduit to my existing electrical service on the house. How deep does the conduit need to be buried, and what bends can or can't there be in the conduit?