If a final hotel bill surprises you with its heft, look for a resort fee. Increasingly, these nightly mandatory charges — which cover pools, Wi-Fi and other niceties — are costing consumers who didn't know they were coming. Even Minnesota resorts have begun following the lead of hotels in tourist towns like Miami, Orlando and Las Vegas, where the fees are among the highest in the nation, according to resortfeechecker.com.

Hotels say the fees, sometimes called "destination fees," pay for guest amenities and reduce the commissions they pay online travel agents; those commissions are based on room rates.

Vacationers say they hide the true cost of a hotel room. Because hotels are not required to include these charges in their advertised room rates, they can blow the travel budget of unsuspecting consumers and make comparison shopping cumbersome.

Uncovering fees ahead of booking requires sleuthing. On hotel websites, they are often tucked away in a "policies" link or don't show up until you click to book. The easiest way to learn of a fee is to call a hotel directly to ask.

Fees can be shrouded on a hotel bill, too; they are sometimes rolled into a line called "taxes and fees," which merges a hotel's take with the government's.

Want to avoid these fees, which can be a flat fee or a percentage of the room rate? Ask before booking if it can be waived provided that you not use the covered amenities. Or hunt down a resort that doesn't charge the fee.

Kerri Westenberg