Can someone please help an Android phone noob out with his battery life?

[PeeingInTheShower]

Okay, so I recently got hold of a Samsung Nexus S device. It is running the stock version of Android 4.1.1 Jelly Bean.
So far the phone has been good. It does lag a bit from time to time however, my primary concern is the battery life. It seems to be quite abysmal compared to what I've heard about other people and their smartphones.

My phone says its been running from fully charged state for 12hrs and is on 19% battery. I'm not a heavy phone user so I'm wondering what's going on. I've made 23 mins worth of calls, played games for less than 10 mins and sent and received some SMS via the native app and What's App. The rest of the time the phone is in sleep and sometimes when I wake it up an hour or 2 later, 10% of battery ( or more) has been lost. I also have screen brightness to Auto instead of full blast.

What's up with that? I read online that some people manage to get great battery life and are able to surf the web and listening to tons of music. I'm weary of doing any of that because I fear the battery will deplete before I get home. Apps like facebook and hotmail I've set not to send out notifications and to manually refresh. I installed an app called Juice Defender to aid me but not to sure about the results.

According to setting>battery it says the top 5 battery suckers are:
Screen (42% ) , Voice calls (13%) , Android System (10%), Cell Standby (8%), Android OS (7%)

I've heard that custom roms and kernels give better batter life but I'm not too sure which ones are reputable and would work with a Nexus S I9020XXKI1.

Please, can you guide me on getting long battery life?
I also don't know how to switch to a custom rom and kernel

[Delight]

install juice defender. lower screen brightness. kill applications which constantly use an internet connection in the background. lower screen brightness.

[Peter]

android phone battery sucks. you should switch to iphone. The battery life lasts a lot longer!
you can try turning off your 3G when you are not using your phone to help you save battery.

[Android Core]

it lags cause JB is a higher verison of Android. Nexus S is 2 years old. Its like a Iphone 3GS running IOS 5. It will be laggy. Old CPU/RAM and hardware wasnt designed for the new software. Just a fact of life.

100% to 19% in 12 hours, thats awesome!!! Smartphones arent flip phones. You need to charge AT LEAST twice a day. I charge in the morning before work to 100%. By the time I get home at 7 or 8pm, its at 30%, and I charge again, or charge and play at the same time...

10% per hour is normal usage. Besides, its Nexus S. It has a small battery. Next, Sleep Mode means the phone is ON, but all its connections are OFF. So no one can call/text you, your data connection, background sync is all off. If your hitting the power button and just turning off the screen, then this ISNT sleep mode. This mode is called Stand-by Mode, means that the phone is ON and ALL connections are still on, so poeple can call you and still text you, and yoru cellular data is still on and background sync is still on. Cellular data and background sync are the reasons WHY you loose 10%/hr of battery and why you still get charged for data on your data plan without even touching the phone

There are many ways to get great battery life, 100-30% in 12 hours, and do heavy surfing, youtube, listen to play lists on your mp3 app, and even do 2-3 hours of Pandora. Maybe even toss 30min-1hr of gaming in there too.. Just remember, the more you MEDIA STREAM--the more battery it takes. MEDIA STREAMs kill battery life.

Apps like facebook and hotmail are pointless in terms of battery life. But, Juicy will get you an extra 20% tops per charge. Its a great app.

Also, try this----Turn your screen down to 30% or 0% brightness... NOT AUTO!!!!!!!!!!! By being on AUTO, eveyrtime you wake up form standby Mode, the screen uses battery to adjust itself to the level of brightness in the room your in!!!! Its like driving your car to yoru next door neighbor 50 feet away!!! Waste of GAS!!! Voice calls :stop talking or text instead. LOL....... Cell standy... you wake up the phone to much from standby mode and put the phone into standby mode to much....LOL.... Android OS along with Android System, since you are a noob, you really cant effective this.... Google "Rooting" "What is Rooting" "Bloatfreezer" and "Titanium Backup and freezing apps"

True that custom roms and kernels give better batter life. But DONT!!! Your still new. Google "Rooting" "What is Rooting" ... after you have mastered yourself on that, the Google "ROM", "What is a ROM", "How do I flash a ROM to Nexus S", "What is a Kernel", "How do Kernels effect phone usage and ROMS"

Make an free account with AndroidCentral.com.... go to the Nexus S forums.... read the sticky thread "Battery Life"...... also, you may Google "Battery Life on Android".. personally, and I;m not being mean here, based on your question, your expecting Android to act like a stupid flip phone. It wont and never will... no matter how your ROM or MOD it. 100-20 in 12 hours is freaking awesome.... and if you want more battery, even with heavy usage added onto that figure, from 7am 100% to 6pm 20% is possible, but your gonna have to learn how Android works. The Android Community can facilitate you. But, we wont teach you. Why???? ""Cause we dont control your fingers. We take no responsibility for your actions""... You'll see those phrases ALOT during your rooting and ROM'ing and MOD'ing life in android.