Activate cheap pre-paid phone to your active billed account
If you're like me, you dread the long-term commitments to replace your aged or broken phone. This procedure does not require any hacking or fancy unlocking procedure. You just buy the phone, charge it, key in phone's MEID and you're up and running on your new cheap but fully functional phone. This may be my favorite phone to date. I replaced my broken old phone for $38 and tax.

Warning: If you activate your phone on the prepaid account plan, it will be locked for up to 6 months, making it useless for billed accounts. Do not click on "OK" to activate it. Do not activate it at all. Wait until you've activated the MEID on Verizon's website before you do anything with the phone.
Buy your pre-paid Walmart phone. You'll want to buy the same network as the one you're trying to activate. In my case, I'm a Verizon customer, so I bought the small cheap LG VX5500 for $38 at Walmart. I bought it at Walmart because if it didn't work, I just return it with very little hassle. Now may be a good time to mention that I was somewhat surprised at the Walmart prices on contract discounted phones.

Get the MEID off the back. On this phone it is clearly marked and the last ID on the back sticker, under the battery. I charged my phone before I started the process just to make sure it took a full charge and to avoid any glitches in activation.

Log into your Verizon online account on Verizon's website. Most other cell phone carriers offer a similar web account tool.

From the account panel, pick the phone nuber/account you wish to activate on the new phone.

Click on activate. Usually this will send you to a screen where you can key in the phone's MEID to activate it. However, occasionally it will just redirect you to some unrelated page or the company's front page. This is what we call a glitch.

If you find yourself at the company's front page, clicking on Activate (at least on Verizon's website) will NOT allow you to activate a phone on your existing account. This is a good way to activate a prepaid or third party phone on a new account, but not useful if you already have an account.
Just go back through the motions until you eventually end up at the activation page. It took me a few times. Their website hiccups sometimes. It's OK.

On the activation screen, simply make sure the phone number you're activating is the correct phone and key in the MEID as indicated by their instructions.
You may be directed to a page where you can choose new services to activate on the phone. In most cases you can simply skip this page or leave it as is. For Verizon customers, this is the only way you can disable web services on your phone to avoid accidental web access. I have asked Verizon to disable this feature on my phones multiple times with negative response, but you can disable it right here when you activate a new phone.

It's probably a good idea to read this page when you're activation is confirmed. You'll notice that it tells you if you're accrued any new charges or modified your plan. In my case the price is clear ($0.00/month) and no immediate fees. It may also be a good idea to capture this page in case you find yourself in conflict with your provider later on about service fees.
The important thing to note here is the number I need to dial to activate the phone. The prepaid phone comes on and asks me to click "Send" to activate the phone. If you do that, you're hosed. Don't! Click the end button to cancel the screen and go to the default phone screen which likely tells you the phone needs to be activated. Here I dialed *228 (as indicated by Verizon's activation confirmation instructions). You'll be asked to hit a key to confirm its activation and it will then cycle the phone with its new settings. Make sure you follow these instructions perfectly. This is the place you're most likely to brick your phone.