Examine background processes that make use of the internet
Cloud computing can be a handy way of backing up files, but the demand these services place on your satellite internet usage can add up quickly over time. If you use cloud based file storage, look into ways of scheduling appointed backup times to off peak or unmonitored hours, so that it's not constantly demanding part of your bandwidth.
You should also regularly check for spyware and malware, as these also might be consuming your bandwidth - aside from the obvious risk they pose to the security of your computer.
Manage the setup for your email account
Though we rarely make use of them, there are lots of options within your email account which can minimise data usage. Default options which are costly in terms of data transfer, such as downloading all attachments automatically, can be changed without compromising your email experience.
Image files in particular can consume a large amount of data, so keeping on top of them in your inbox is a must. Also, consider the files you send over email. Default settings on Image files will often be on high-resolution, which means big-data packages. This is unnecessary if you're just exchanging some snaps with friends or family, as they don't need to be edited in detail later on. Simply lower the settings of the file to under 1MB, and save yourself the usage.
While sticking to these tips requires a little effort, it's preferable to unnecessarily hitting your internet data limit.