1. Make sure the area in which you work is well ventilated as some of the materials involved in oil painting can be quite toxic.
2. Lay your oil paints in the same order each time you paint so that eventually you will be able to pick up the next colour intuitively. This will lend to a smoother painting process.
3. When deciding on an under-layer, choose a colour that has pigments of lead, cobalt or manganese because these dry quicker. You can also use acrylic paint layer which dries very quickly.
4. Linseed oil dries the most quickly of all the oil mediums so it’s good for under-painting. Rather use Poppy oil if you are painting with light colours as linseed oil can sometimes yellow.
5. Remember that the lower layers of oil draw moisture from the layers that are on top of them; make sure that the top layers have more oil in it than the bottom layers. This is called ‘fat-over-lean’ painting. Top layers dry quicker so this will prevent cracking in the paint.
6. If you want to be budget friendly, use student oil paints for your under-painting and higher quality paints over them.
7. To clean away a layer of oil use alcohol.
8. When it comes to brushes: nylon brushes are better for acrylic painting. Use brush cleaner and preserver to keep your brushes in good shape.
9. Hold your brush in the middle or towards the end rather than near the bristles. 
10. Dry your oil painting in a lit area. Darkness can cause the oil to create a colour-yellowing film.

Have a look at our other guides: 10 Acrylic Painting Tips and  10 Watercolour Painting Tips.