Pastel techniques are little challenging as the medium is mixed and blended directly on the working surface. In other painting mediums, you can test the colors on palette before applying to the surface. It is advised to experiment with the pastels in the small scale on the rough piece of paper before applying to the final composition.
Some of pastel techniques are similar to water color techniques as well as charcoal painting. You have to be more careful while using pastel techniques because the pastel errors cannot be covered the way paint can be painted out.