Always clear around the tree so that you can fell it without obstacles. Also clear in the intended felling direction. Small trees, shrubs and branches could obscure the line when you determine the direction of fall.
Cut down obscuring shrubs and small trees in your path of retreat, about 45° behind the tree in both directions. Clear the ground of branches and other obstacles.
Pruning makes the felling safer by removing low branches and twigs which are in the way. The safest way to prune is to work with a pulling chain (underside of the guide bar) from the top down.
Use the trunk as a barrier between you and the chainsaw. Never prune higher than shoulder height.