The best way to define a 'pay as you go' cell phone plan is to first define a standard plan.

Though standard plans differ, most involve a mandatory long-term contract of 1-2 years, a credit card, and a minimum monthly fee of about $20 - $35 U.S. dollars. For this price approximately 200 - 300 minutes are purchased. You can buy more minutes for a higher monthly fee. If you go over your allotment you will likely be charged a premium rate for each additional minute. If you don't use all your minutes they normally do not roll over. That is, you lose them and start over the following month.

Standard cell phone plans have their perks, however, over 'pay as you go' plans. They often include free weekends and evening calling; meaning calls made during this time do not count towards your allotted minutes. For a small fee you can add options too, like free calling to any other cell phone that uses the same service; or free calling to certain cell numbers on other services -- friends or family members. Carriers have their own combination of features to choose from. In fact these plans can present so many options and contingencies that some people can find it confusing.

Finally, standard cell phone plans usually offer a high quality free phone with the plan or more expensive phones at deep discounts. This plan is probably the way to go for anyone who uses a cell phone more than 90 minutes every month.

'Pay as you go' plans work completely differently. For starters there is no monthly fee or contract and you don't need a credit card. Instead you can buy a phone card from the market which is like giving the carrier money towards your account. You only need to add $20 credit to the account every 90 days to keep it active. However, minutes are billed against that at about $.25 each, a higher rate than a standard plan. And there are generally no perks.

A 'pay as you go' plan first requires that you buy a cell phone made to use with this type of plan. You can purchase pay as you go phones from stores like Target. The phone needs to be made for the carrier you will be using. If you want to use Virgin Mobile, for example, you'll need a Virgin Mobile phone. If you don't have a credit card or don't want to use it, you should also purchase a phone card for that carrier. They cost anywhere from $20 up, and are just plastic cards used to add credit to your account.

Once you buy the phone, signing up is easy. Just call the carrier's number listed in the phone manual. The representative will ask for the serial number off the phone, then will assign it a cell number. Some carriers automatically credit your account with $10 for signing up with them, but if not, you can add $20 to your account with the phone card you purchased. Your account is recorded using the cell number, so you don't even have to give the company your name!

Cell phone minutes are deducted from your available balance. If the balance reaches zero before 90 days have expired, you will need to buy another phone card to add more credit to the account before you can make additional calls. This is why it is called 'pay as you go.' If, on the other hand, 90 days passes and you haven't used all your credit, you will need to add $20 dollars anyway to keep the phone active, but your existing balance accumulates. You don't lose it if you don't use it!

If you do have a credit card you can opt to have the carrier keep it on file and automatically debit it every 90 days to save you the trouble of remembering. Optionally you can "top off" the account yourself anytime by simply accessing the top-off menu on your cell phone.

The advantages of a pay as you go plan are no contracts, no credit card requirements, and no monthly fees. Minutes are typically more expensive, however, plus you must buy a phone and there are normally no perks. Free weekends and evenings might be offered for short periods of time as promotional campaigns but as a general rule these plans tend to be very straightforward.

A pay as you go plan is popular with teenagers who lack credit cards and adults who only use their cell phones minimally and therefore can't justify the cost of a standard cell phone. It is probably wise to talk to several carriers about your particular needs and the choices they offer before deciding which plan is best for you.