I have a plumbing question?

I am installing a new shower in an area where there was none. I am building the shower up on a platform so the water will have enough pitch to flow to the sewer line. My question is what do I have to do to keep the odor of the sewer line out from the drain through the drain line to the sewer, which is one continuous run. I am familiar with the P-traps in sink application but not with this application. Also, just in case I can't get the right pitch for the drainage, what do you recommend (pump) etc.? and how do I do it?