1. Observation is the number one key to realism drawing.
2. Try to see your drawing as different piece of lines, shapes and tones.
3. If you are beginner always try to get as many different references as possible before starting drawing.
4. Drawing slowly step by step on each small step you`ll begin to understand how to draw objects.
5. Keep works in progress, do not give up just because the result didn`t turn into what you expected. Drawing is a process and takes time.
6. Be objective when you looks at your work, if you see areas that can be improved turn it into a goal for the next drawing.
7. Start with practicing to draw things you like and as always you learn the most from things you really enjoy.