Dropbox is a robust independent file syncing tool (which Apple once tried to buy) that recently hit the 100m user milestone. It’s arguably the most popular cloud service around, and for good reason. One of the key advantages of Dropbox is that it’s so easy to use—you simply set it up and then forget about it — but if you dig a bit deeper into the application you’ll find that it has more strings to its bow than you might have realized. 1. Get as much free space as you can: Dropbox gives you 2GB of free space, but you get an extra 500MB for every friend you refer to the service. Dropbox also gives you 125MB extra just for tweeting about your love of the service. Keep your eye on the official forums too; in the past many gigabytes’ worth of bonus space has been given out for testing beta versions of mobile apps and entering Dropbox competitions.