Determining whether it’s good or bad to buy a prepaid item depends entirely on what’s being offered. There’s no universal advice or rule of thumb. Here’s a guide to some of the common forms of prepaid offers consumers might encounter, separated into whether you should consider buying them.

Cell phones. Unless you want the capabilities of a smart phone with Internet access, a pay-as-you-go prepaid wireless phone is a great idea and can be far cheaper than a cell phone with a monthly contract, experts say. That’s especially true if you use only a few hundred minutes per month. But even moderately heavy users can reap savings, says Consumer Reports magazine.

With a prepaid phone, you buy an inexpensive phone and load minutes onto the phone as needed. You can buy minutes online or at retail stores in the form of a prepaid phone card that has a code you type into the phone. Taxes and fees are included in the price of the minutes. A few downsides: The phones are not the most current models, and minutes expire after a set period.

Discounts. All sorts of services, from insurance to pest control, might offer a discount for prepaying in a lump sum upfront rather than monthly. This is generally a good idea nowadays if you can afford it, assuming you can get money back for any unused portion of the service if you discontinue it. Why? Typically, you would compare the discount with how much interest you could otherwise earn in a safe account, such as a bank account. But interest rates are so low now that prepaying for services will almost surely reap a higher return.

Credit cards. A couple types of cards can fall under this category. One is a secured credit card where you deposit an amount, say $500, and you can charge up to that amount. This is useful for young people trying to establish a credit history or for those recovering from damaged credit and personal bankruptcy. The key is to find a card that reports to all three major credit bureaus, which will start improving your credit scores if you pay on time, said Liz Pulliam Weston, author of “Your Credit Score.” A secured credit card that converts to a regular credit card after a period is ideal, she said.

The other type is a refillable prepaid credit card that acts like a debit card. They have the advantages of credit cards, such as being able to book a rental car, without the downsides of overspending or finance charges, Weston said.

The downside with all these cards are the fees, Weston said. For example, a prepaid card might have a one-time $20 processing or application fee, plus a fee of $5 per month.

Gift cards. They are convenient, but a $50 gift card is inferior to a $50 bill that can be spent anywhere. Plus, some gift cards have fees.

Tuition. Prepaid tuition plans have helped millions of families in the past, but consumers nowadays need to be wary, said college-savings expert Joe Hurley. That’s because states, which sponsor prepaid 529 plans, are suffering budget shortfalls and might not be able to honor pledges to pay for future college costs, he said.

About half of the original 18 states that offered prepaid plans have closed their plans to new enrollment. Of the remaining, just four plans are guaranteed; that is, backed by the full faith and credit of the state. (Those states: Massachusetts, Mississippi, Texas and Washington.)

Prepaid funerals. Almost never a good idea, said Joshua Slocum, executive director of the Funeral Consumers Alliance, which attributes one-third of complaints it receives to prepaid funerals.