For those of you with a filthy mind, Mojito literally means 'something wet'. There's a joke in there somewhere, but we'll rise above it for once.
I favour using sugar over sugar syrup, as the hard crystals help crush the mint and release the flavour into the rum.
Also, I like to garnish with an almost ridiculous amount of mint brimming the surface, so that you get a full whack the aroma as you bury your nose into the glass.