How to limit data usage on IPhone 4?

So I'm going onto this new plan where I only have 250 MB of data, and I was wondering what some ways are to limit my data usage? I have wifi at home that it automatically goes to, but I use things like maps and Facebook and safari to look things up. Any tips?

Thanks!

The best thing I can suggest for you to do, is upgrade your data plan. It's pretty much impossible to have a smartphone with limited data usage when you use, Safari, Facebook, Apps etc. If you want to see how much data you're using, you can download an app assuming that your service provider has one. From their app, you can view your data usage.

I'm not sure if this works on Verizon or Sprint, it should, but it definitely works on AT&T:
Go to Settings > Phone > (AT&T/Verizon/Sprint) Services > View my data and Msg

It'll show you how much you've used and how much you have left.

I used to have the limited 200 Mb data plan on my iPhone, so what I did is I disabled all push notifications, because that uses internet. I also didn't watch any YouTube videos or used music streaming apps like Pandora or Spotify. I just browsed and used Facebook, and I had some left over. I could watch a Youtube video or two, and I would be fine. Also, don't download any apps.

Feel free to do all of the things you love about the iPhone while you're on Wi Fi, but just be aware of when you're not.