there not that easy to screw up, just keep an eye on whats going on with them, if you swithc off two sided lighting any black faces have the nromals facing in the wrong direction, so select them and set to face to get them the right way.

They used to get me a bit wound when I started up as I never knew what was going wrong with my models when I had black splodges at render time, but now I dont get them in my models at all, think its just experiance and using the tools correctley, as I got them all the time using the extrde commands!