Only astrally project if you are in a stablemood (if you are clouded by negative thoughts and feelings, you will attract negative entities).
Donot astrally project if you are on drugs - this will take you to a lower plane of disorientation and will be less vibrant.
Just in case, ask your guides to protect you (as there can be malevolent beings).
Ideally, only do it if you believe it will be spiritually benefiting (it is not a necessary part of spirituality)rather than a source of entertainment.
If you do it incorrectly, it could lead to sleepparalysis.
You cannot get possessed by malevolent entities, but they can get attached to you.
Always surround yourself with nurturing and higher vibrational energy, and avoid beings with darker/clouded auras as they tend to be less benevolent (but not always - it is just a precaution if you are new to astral projection).
Avoidfear - do not worry that you can die while astrally projecting (as you will not), if your astral body senses danger it will immediately return to your physical body.