The first consideration for this task must be safety. The safety of others in the site and yourself as well as the surrounding area must be considered.
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Have you the right tools for the job?
Check for obstacles to felling, particularly other trees, overhead cables and fences.
Check that other people stay at a safe distance at all times while felling is taking place.
Make sure that you and others know the danger areas and that your safe exit path is clear.

Also see more information on felling.