f you are installing a new sewer like you will want to set the "grade" which is also known as the pitch to the local plumbing code. However in many states the code is 3/4" per 3 - 4 feet.
Water and solids need to flow downhill for the sewage line to work. So when installing any type of drainage line, always make sure to set the correct pitch to prevent drainage and sewer blockage problems later on. Often the sewer lines are installed with backwards fittings, bad pitch and even on non tamped ground causing the pipe to bow and sometimes even crush.
Installing a sewer line is something you want to leave up to a licensed plumber and in almost every state it's the law as well.