Oil Painting

I've never worked with oil paints before, so this semester's been a bit of a struggle. One of the classes I'm taking is Still Life Painting. At my school, oil paints are the preferred paint medium, so learning how to use them is crucial. I do think I'm getting better, but I still need a lot of practice. I'm not a painter, but this class will definitely help me improve with digital painting. Here are some paintings from this semester so far. They were all done in class (about 6 hours long). The first is the most recent, then it continues on, down to the oldest one.

Have you ever worked with oil paints? If so, I'd love some tips and tricks on using them.