Internet usage help!

So, I decided to downgrade my broadband from 30mb to 10mb, as I didn't really need it, but on the 30mb the usage was unlimited but on the 10mb deal the usuage is 120GB, what I want to know is that a decent amount?

What would I have to do to exceed that? Any help would be appreciated.

EDIT: I only use my internet for browsing, youtube, various websites like that, I don't download DVD's or anything, also, does your download usuage take into account online gaming, watching online vids? Or is it just actual downloads? Like off torrent sites?

Download usage is all information transferred from your ISP to your modem. So say you make a google search, although the download may be minuscule, it still counts within your monthly usage. That's how it works in Australia so don't flame me if you have it differently.

120GB should be more than enough for basic internet browsing if you don't torrent anything.

What happens if you go over your internet usage? Does your ISP let you know? Nice one for the info, Ghost.

You're ISP should provide some sort of online service where you can track how much data you've used for the period.
Some ISP's will incur excess usage charges which are extremely expensive so you need to watch out for that, but some ISP's (such as mine) will just slow your internet down to 64kbps (dial up speed) for the remainder of the billing period. You'll have to read the details of your plan to see what your ISP does if you go over the limit.