I'm a guy that has worn many earrings in my time and just re-pierced my lobes.
I think if you are going for a masculine long earring look. You will want to go for short lengths, nothing too long. Also thing's like crosses at the end of a small chain will look masculine. Sometimes it looks more masculine to have a long earring on one side, instead of both sides.
I am a feminine guy though, so I wear anything that is to my liking. I wear flowers, butterflies and longer earrings. Of course I usually wear hoops or huggies, with a diamond stud in my nose.
As a general rule guys with earrings usually wear studs or huggies, as longer earrings make you look more girly. There is little you can do to get away with that, but if you are comfertable in your own skin like me, you should have no problem wearing longer earrings.
Another masculine trait would be to stay away from color, keep it silver, gold or black.