How do I cut away from septic tank and connect to new city sewer line?

I'm planning to connect to a new city sewer line from an exisiting septic tank line. I plan to cut in to the drain line from the house and route the line into the connection that the city has recently installed. I know I need the line to have a slight fall to it and that I need a back flow valve in the line. Is there anything else that I'm not thinking of? I know I need permits and to check for buried lines also. Thanks