Sink hook up in shop?

I have a garage shop about 30 feet from my house, Iv'e installed me a sink inside of the shop. I have a water speaket right beside my shop that Im going to tap into for my regular water for my sink. Then Im going to tap in at my house kitchen sink line for the hot water. My question is the drainage problem im faced with. My shop is level on the ground with concrete under neath. It's a metal building, so all the pipe lines are going to be coming from outside the tin. But far as the drain, dont I have to run a pipe going down hill all the way to my sewer? Or could I run the drain pipe level or up somewhat for the water to flow and drain? The reason I ask is at my house I noticed the drain pipe is running level then down so I guess it can flow, since it's no pressure on draining water. Only water being used? So how can I run this drain pipe for the sink in my garage? does it matter which way it goes as long as I tap into a sewer line?