If you're on the hunt for a cheap smartphone, get ready to pull the trigger. The best smartphone deals of the year crop up just about now -- as big-box retailers and cellular carriers try to grab your attention during the Black Friday/Cyber Monday shopping craze.

Smartphone makers, led by premium brands Apple (NASDAQ:AAPL) and Samsung (OTC:SSNLF), generally keep a tight grip on pricing, leaving budget-oriented shoppers with few options for discounts. Even Black Friday and Cyber Monday smartphone deals come with heavy restrictions and extensive fine print. But if you can meet the requirements, you stand to save. Here are four ways to score a cheap smartphone now.

Smartphones on display in a store

Image source: Getty Images.

1. Switch carriers and trade in your phone

Cellular carriers love to woo you, and your phone, away from their competitors. So, if you're in a position to switch carriers and trade in your old phone, you have the best opportunity to save. First, check-in on your contract. You'll need to know if you've fulfilled the contract already and, if not, what the prepayment penalty is.

Then, make sure you actually own your phone. If you're making monthly payments on the phone itself, you've either financed the purchase of the phone, or you're leasing it. These days, leasing agreements are more common, and when you're on a lease, such as the Flex lease from Sprint or an installment plan from AT&T, you won't own the phone even after you've finished with the payments. In that case, you can't trade-in the phone at a different carrier.

If you do own the phone, you can switch carriers and trade it in to earn credits on the purchase of a new phone. Know that these credits are usually doled out in monthly increments over 18 or 24 months. That means you'll have to sign a lease agreement on the new phone, and the monthly credits will offset your lease payments. If you cancel your contract early, you may have to pay back any credits you received for your trade-in.

Here are four of the trade-in deals running this holiday shopping season:

  • Get a free iPhone from T-Mobile when you activate a new line and trade in an iPhone.
  • Get up to $700 in credit toward a new smartphone when you switch to AT&T and trade in an eligible device.
  • Lease an iPhone from Sprint for free when you switch to Sprint and trade in your old phone.
  • Get up to a $400 credit when you purchase a Samsung Galaxy S10 from T-Mobile under an equipment installment plan when you trade in an eligible device.

2. Switch carriers without trading in your phone

If you don't own a phone today, you can still access some nice smartphone deals by switching to a new carrier. These deals, designed for new customers, are also available to you if have no service, or if you want to switch from a prepaid plan.

As with the trade-in deals described above, there is fine print. First, check your existing contract to see if you can cancel without incurring additional fees. Then, ask about the contract requirements with the new carrier. You usually have to stick around for 18 or 24 months to avoid penalties.

If you're ready to switch carriers, here are some deals to shop:

  • Get up to $300 in bill credits when you switch to AT&T.
  • Lease a Samsung Galaxy S10 for free when you switch to Sprint.
  • Save $250 on a Google Pixel 4 at Best Buy with activation.
  • Get a $400 Target gift card when you purchase a Samsung Galaxy S10 and activate it with AT&T.

3. Add a new line to your plan

Cellular carriers will offer buy-one-get-one deals to encourage you to add a new line to your existing plan. That works out well if you want a new phone and you've promised your 12-year-old daughter that she's getting one, too.

T-Mobile currently has a buy-one-get-one deal on the Samsung Galaxy S10. And with Sprint, you can lease two iPhones for the price of one. Both deals require you to activate a new phone line.

If you have AT&T service, you only need to get one new phone and one new line to qualify for up to $300 in bill credits.

4. Upgrade or trade in your existing phone with your existing carrier

What if you don't need to add a line and aren't interested in switching carriers? You may be able to save with an upgrade or trade-in deal directly from your carrier, or from retailers such as Walmart and Best Buy.

If you financed your current phone with a purchase installment plan, your carrier will ask you to pay down most of what you owe. AT&T, for example, requires installment plans to be 80% paid off before you can upgrade. If your phone is leased, and it probably is, you'll also have to turn in the phone.

The most compelling upgrade deal we could find this year is available at Walmart. You can get a Walmart eGift card valued at up to $450 when you upgrade to select Apple and Samsung smartphones on your AT&T or Verizon plan. To qualify, you need to finance the new phone on a 24-month or 30-month installment agreement.

T-Mobile is also offering a trade-in credit of up to $400 when you purchase a Samsung Galaxy S10 under an equipment installment plan. This deal is available to existing Sprint customers, so you wouldn't have to switch carriers if you already use Sprint.

Remember to read the fine print

Cellular carriers structure smartphone deals in the hopes of luring you away from competitors and then keeping you around for a while. Before moving on any smartphone deal, read the fine print, and make sure it's worth it. Changing your mind later may require that you give up your smartphone and your service -- and then pay a fee to boot.