Some people leave a little air at the top of the syringe. I just get the ones with the rubber pin that goes down the nozzle to where the needle begins. The Exel 3ml luer lock tip model. Look at the rubber stopper:
That's the kind you probably want to get.
I suggest you go on YouTube and watch a lot of videos on how other people draw syringes and shoot intramuscularly. It'll help you learn what to do. I'll tell you this much, the first time I did it, I sat on a toilet for like a half hour getting the nerve to do it. And then I shot in my quad and fell to the floor coughing up a lung.