A lot of the settings in the GUI you won't need to touch.

I do usually adjust the camera/film settings to set the focal length, exposure, f-stop, I also like to set the output path and output name to a specific name for different projects.
And depending on the scene and lighting used it is sometimes good to adjust the integrator in the renderer tab, it can help if your scene ends up with a lot of fireflies; I like to use distributed path or direct lighting.

Software: OS X 10.8 - Poser Pro 2012 SR2 - Luxrender 1.0RC3 - Pose2Lux
Hardware: iMac - 3.06 GHz Core2Duo - 12 GB RAM - ATI Radeon HD 4670 - 256 MB