[link=http://www.rcaerobats.net/trim_chart.htm]Go here[/link] and look at up/down thrust #1+2, and side thrust. It's about half way down the page. Note that the chart is meant to be followed in order.

Planes generally need right (and down) thrust. If you're the pilot, the engine should be pointing to the right and down. This all stems from the fact that the prop is sending swirling air over the plane and control surfaces. The top of this link talks about using mixes as another way to compensate for the spiraling air. It's up to you if you want to use mixes or make mechanical changes.