For years I've been intimidated by the idea of making my own Simple Syrup--I think because it involved sugar and boiling water I assumed it was as complicated as candy making, with monitoring of temperatures and so on. Nothing could be farther from the truth, it turns out. You just put equal amounts of sugar and water in a saucepan and heat it until the water boils and the sugar dissolves completely. You don't even have to stir it (though, if you're like me, you'll give it the occasional stir just to feel like you're doing something). Then cool and store in some convenient container (I use an old port wine bottle with a cork). Store it in the fridge.
For determining what size container you'll need, know that 250 ml (1 cup) of water and sugar each makes 300 ml of syrup. Science! That's perfect for that little 375 ml port wine bottle.