Inexperienced people should preferably not work with tools without experienced supervision. Aside from using the tools in manners they were not intended for and potentially damaging them, an inexperienced user might seriously hurt himself.
There are some basic safety guidelines one can follow to ensure user safety when working with any tool. Though very special care needs to be taken where blades are involved, especially if they're power-driven.
Keep hair and loose clothing away from all power tools, because these might get caught in shifts and rotations. Always wear safety gear, especially safety glasses to avoid flying bits of the material that is being cut from coming into contact with your eyes. Also wear safety gloves to protect your hands from the sharp blades and the heat that is generated from the friction between the material and the blade.
Though it is advisable to avoid excessive heat generation on the cutting surface in general. Use oil or other coolants, especially when you are working with metal, since lubricants will help keep the surface cool and might help cast away excess material.
Clear chips and cast off material away from the cutting area frequently to minimize the amount of loose material that could potentially fly about while you are cutting. Cast off material might also cover the area you are cutting and prevent you from seeing what you are doing, which increases potential for errors and injuries.
You should hold the saw firmly and apply sufficient pressure to enable the saw to cut freely, instead of bouncing or rebounding off the cutting surface. Operate the saw at the recommended speeds for the material being cut and the diameter of the saw.
Importantly, select the right saw for the job and read instructions or ask an experienced operator's advice if you are unsure of how to use it.