I've faced this problem before and I tried my best to control it. Here are a few tips from me
1) Get some browser other than IE which offers you high control over what all you can block from the internet
2) Block Pop-UP Ads
3) Block Google Ads
4) Disable Images for your General Browsing and Enable them only for a few websites which you think are terribly important.
5) Keep a Track of what you download. Have an account of the major downloads you've made
6) Since you have 1 GB/month, divide it by 30, you get 33. Make sure your daily consumption is around 33 MB.
7) Continuosly check your BW usage, perhaps if you feel in the middle of the month that it has gone high and you find it;s 800 MB already, then reduce your usage for the rest of the month.
8) Important - Disable Flash Images 1000%, they use Bandwidth LIKE HEck.
9) Reduce Google Earth - If it is your buisness, okay but for a hobby if you wanna check out all kindsa places then get a better broadband
10) Use Google WebAccellarator or some tool which loads cached pages. Onspeed is paid BTW.
Don't think your cutting all in Life. Try this for a week and see how much you are using. If you feel, you can use more, then change. I'm talking about this in experience only. Once Upon a Time I had Iqara Connection and I successfully used 500 MB for 4 full month.
Hope this Helps you
Regards
Retro