Q: How to close apps on my iPhone 3G

First restart your phone by holding down the on/off and home buttons until you see the Apple logo, the try it.  Once you see the open apps hold you finger on one until the start to wiggle and a red "x" is shown in the left corner of the app, touch the "x" and the app will close. 

Multitasking with 3rd party apps is not supported with the iPhone 3G, so there is no recently used apps bar or dock available with iOS 4 for the iPhone 3G.

It's freezing becouse of the iOS, you need firmware 3.1.3 on 3G to work properly. I upgraded to 4.1 once and i had the same problem.

If you want to close a running App, such as Maps or anything else that constantly updates itself, open the App, press the power button until the Power Off slider appears, then hold the home button until the home screen appears. The App is then switched off.

The Maps app does not run in the background so does not constantly update itself.

Very few apps run in the background.

When you double click sometimes it's triple to get the recently opened apps show on the bottom, sometime they're still open, hold down on one until it shakes and has a Minus sign then just click the minus sign.

That does not mean the apps are open and running since very few 3rd party apps run in the background. The number of 3rd party apps that run in the background are very few and far between. For the most part overwhelmingly, this means the apps were recently used only.

http://support.apple.com/kb/HT4211

http://whenwillapple.com/blog/2010/04/19/iphone-os-4-multitasking-explained-agai n/

As Allan has already pointed out, and other have seemed to ignore... the 3G can NOT multitask. There is nothing to close...