It's always smart to do the math before you apply for a balance transfer card to see how much you'll need to pay each month in the allotted intro 0% or low-interest offer time period.
For example, let's say you're currently carrying a $3,000 balance on an existing card with a 22% APR and paying $200 a month. It'll take 18 months to pay off that debt and you'll end up paying $541 in interest, or a total of $3,541.
If you transfer that debt to a balance transfer card offering a 0% APR for 18 months with a 3% balance transfer fee, and keep your $200 a month payments up, you'd just pay $90 for the balance transfer fee and have your balance paid off in 16 months.
So, you'd be saving a total of $451 ($541 that you'd pay in interest charges if you don't utilize a 0% APR balance transfer deal, minus the $90 balance transfer fee for the new card) and pay off the balance two months quicker.