There a lot of things you can do to help your battery drain.
The first thing I always suggest is turn off 4G if not using it.
Next is turn off wifi unless using it.
Also there are apps to control the way the phone syncs, which can save battery. I use an app called Auto Sync widget by Curvefish. It turns all sync off until you toggle the widget. If you rely on emails and such, and need to be notified, try tasker (paid) or Syncer (free) which will allow you to schedule timed intervals in between syncing. Remember when the phone is syncing all the time it's using data and the 3G radio is a bit of a battery hog.
I turn the screen brightness down to about 30 to 40%. Deselect autobrightness. Another thing is disable live walpapers.

There is a battery tweaks thread that may help:

http://androidforums.com/evo-4g-tips-tricks/150799-battery-tweaks-htc-evo-4g.html

Read through this and if you have any questions please ask away. We're here to help!

 

I got the Evo 2 days after it came out - great phone, I still use it.

Had these exact same problems, Katie.

So, follow the battery tips that Granite pointed out - and also - do not use a task killer.

My advice, let's get you all configured to get the best performance, and then go ahead and do the facelifts and other fun tweaking.

While others argue, I still say the Evo was The Very Best Phone of 2010 and I think you're going to enjoy the heck out of it.

Welcome to the Evo, and let us know anything we can do to help!

 

Congratulations Katie, you got a great phone.

I too got my EVO shortly after launch, and have not yet seen anything compelling enough to warrant upgrading it.

Now if Sprint was to pick up the Galaxy Nexus Touch, I might have to take a look!

 

If you must use data, use wifi. Uses much less battery.

Add widgets to one of your screens by pressing on a spot and holding, then hit widgets, then scroll down to settings, add Mobile Network (it doesnt say it, but its 3G), then do same for WiFi, 4G and GPS. Mobile Network is 3G. Turn off stuff when not using it. Think all but Mobile Data widgets are on one of your screens by default when you bought the thing.

At home or work, I can go all day using WiFi. I only use 3G Mobile Network Data when in car or somewhere without WiFi. No 4G in my area.

With 3G Mobile Network data, 4G, GPS and WiFi off, you will still receive calls and text message. You may not receive pictures or video without some sort of data on, nor Facebook notifications. Will need some sort of data source to get those.

But I suspect the Mobile Network (3G) is the culprit. Turn it off when you dont neet it to browse the net, or to use Market or any data app. Use WiFi when able over 3G Mobile Network.

WiFi, 3G and 4G are all data/internet sources. Doesnt matter which you use if all are available. 4G is faster than 3G, but uses more battery. Your speeds on WiFi will vary depending on source.

From least to greatest battery suckers... WiFi ... Mobile Network (3G) ... 4G. Dont forget to turn off GPS if you dont need it.

 

And if you do need and use 3G, go ahead and turn off Mobile Data Always On.

You'll still get your mobile data, the radio just won't be on constantly.

 

get an iphone

(i kid )

I think most of us had similar problems you are having when the phone first came out. This is an extremely powerful phone with an extremely middle of the road battery. That being said, all is not lost- the stickys here have great battery tips and everything people said above is true.

first day out in the real world with my e4g i had killed it by 2pm.
of course i was running 4g, gps, bluetooth and using the crap out of it...

make sure you turn the stuff of that you're not using.
i think the wifi radio is more energy-efficient than the 3g (someone please correct me if this is not true) so i leave it on all the time.
wifi is WAY more efficient than the 4g radio which will kill your battery.
gps will absolutely destroy your battery too.
if you're using gps for any length of time, you're probably in the car - plug it in.
autobrightness or setting brightness/timeout
avoid background animations. they look pretty but they use more battery than static screens.

4g is awesome if you're in an area that supports it but most of the time i find myself not bothering to turn it on... you would think that would bother me since 4g is right there in the title, but hey - i think people actually use the PHONE part of their smartphones what, maybe 30% of their total usage? i'm more annoyed about the "mandatory" $10 nonsense but that's a gripe for another thread...

there are a billion great apps out there - you have to just look and try them out or give us an idea what kind of apps you're looking for.

if and when you decide to root the phone there is also a wealth of info for that too - and that opens up even more options for keeping your battery in line.

i use the heck out of my phone and i routinely get away with 24+ hours of moderate use without any loss of functionality. i used to be chained to chargers - home, car, office. lame.

superuser abilities to reset battery calibration, run apps like Green Power, adjust the cpu, install different roms and a few other minor tweaks, i'm much happier now.

good luck and congrats on the new phone

 

Hi Katie123!!

Glad you've stopped back in.

Android uses a different memory structure and os than windows. Windows based systems are resource hogs, and killing tasks is a great way to improve performance. Android is based on Linux, and the OS handles tasks differently. Android takes apps you frequently use and loads them into your memory for fast easy opening / retreval. When the system needs resources it "closes" an app on the open list to make more memory available. It really seems backwards, but android does a pretty good job of managing memory / resources without a task manager / app killer.

Here are a few articles you should check out, there is a lot of info on this subject that may help you understand a little better.
http://androidforums.com/tips-tricks-evo-4g/85554-task-killers-must-read-new-android-users.html

You said your battery gets hit pretty bad in school, correct?
Do you have good signal while in school?

Having poor signal will destroy your battery, no matter what steps you try to improve it. Getting a 200mA battery will help absolutely, but make sure if ou get one, you properly charge the phone once you install it. Let us know if you do get a new battery and we'll help you then!

Let me know if you have any questions!