Today is preorder day for the new iPhone 4S. The phone features an improved camera, faster processor and other improvements. You can read more about it here.

The iPhone 4S streets on October 14. A limited number of them (huge, but limited) will be available on that day. To ensure you don’t have to wait several weeks to get yours, you should preorder it now. Right now. Go!

Here’s what you’ll need, what you can expect, and some of my own experiences in getting an upgrade. Read through to get some handy upgrade tips.

The easiest way to preorder your iPhone 4S is online. You can upgrade through Apple, AT&T, and Verizon here in the US. If you’re with Sprint here, you can upgrade your current device by ordering online as well. Here are links to the preorder pages:

Apple

AT&T

Sprint

Verizon

You can also order srtaight from your iPhone using the Apple Store app. | Apple Store - Apple

Be prepared to pay $199-$649 for a 16GB, $299-$749 for a 32GB, and $399-$849 for the roomy new 64GB. Apple and AT&T will both put a hold on your credit card for the full amount which then charges when the device ships. I suspect that Verizon and Sprint will do the same.

If you bought your iPhone 4 on its first day on AT&T, you’re several months short of the 24 month contract renewal to be able to upgrade at the one, two, or three hundred dollar level. If you spend a lot of money with AT&T and your account is in good standing, AT&T is offering an early upgrade for a reduced rate, but odds are you will have to wait anywhere from 2-6 additional weeks before you get the phone in hand.

For example, I bought my iPhone 4 in June, 2010 when they were first released and signed a two year service contract. To get the upgrade to the 32 GB iPhone 4S, it would cost me $549 — a $200 discount off buying the phone outright — and I would be eligible to get the phone on November 30.

If you’ve still got a lot of time left on your AT&T contract or you’ve been late on your bill, you may have to wait a while or pay the full, unsubsidized price for a new 4S.

If you are a Verizon US customer and bought the iPhone 4 when it was released, you’re pretty much limited to dropping the cash for the full price of the 4S right now. I spoke with a local Verizon representative here and unless Verizon announces a “roll-up” upgrade program (which they haven’t yet), you are eligible to upgrade your iPhone 4 after 12 months. That means you won’t be eligible to upgrade your device until February 2012.

Tips For Getting an Earlier, Cheaper Upgrade on AT&T

If you’re like me and immediately went to the Apple site to check upgrade eligibility, you were probably informed that you did not qualify immediately for any upgrade pricing, and qualified for reduced iPhone 4S pricing — $200 off the full price — with a November delivery date.

Call AT&T Customer Service to request an early upgrade. If your account is in good standing, they might be able to move your upgrade eligibility date up a couple of months, making you eligible for the $200 discount now, even though you still have over 8 months left on your current iPhone 4 contract.

If that doesn’t work, go to an AT&T Mobility Store to order an upgrade. Not an authorized reseller, but an actual, company-owned store. I found out that AT&T Store employees may have better luck in getting you better upgrade pricing. Plus, you get to plead your case in front of a real live person, not just a voice or two on the phone.

Should You Upgrade to the iPhone 4S?

If you currently own an iPhone 4, have a lot of time left on your contract, and it will have to pay full price for an upgrade, probably not. The iPhone 4 is still an excellent camera and iOS 5 runs great on the 4. You won’t have the Siri Personal Assistant, but can still take advantage of all of iOS 5’s other features. The iPhone 4 is still a sexy, fast phone. Plus, you’ll be in great upgrade position when the real iPhone 5 is released, probably in a year or so.

If you’re a current iPhone 4 Verizon customer, travel often and need the world phone functionality of the iPhone 4S, the full-price investment to upgrade may be worthwhile for you.

If you own any older iPhone, such as a 3GS, 3G, or 2G and have been with AT&T for a while, you probably qualify for the sweet, low upgrade pricing of $199, $299, and $399. It’s a no-brainer — upgrade if you are entertaining the idea and your budget can afford it. The iPhone 4S is so much more advanced than the devices your are currently using and the camera is so superior to even the iPhone 3GS, it will feel like your first iPhone all over again.

If history is any guide, there will be lines and waits when the iPhone 4S streets next week. Preorder now to minimize any delays. Good luck!

Got any other tips for upgrading? Are you a US Verizon customer? How about iPhone 4 owners in other countries? Share your tips below.

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Disclosure: These are my recommendations for ordering a new iPhone 4S. Life In LoFi gets no compensation of any kind from the links or purchase recommendations in this post.