As life on the road gets more complicated and marketers come at us from new angles, it's often hard to know what free perks are available where. It's even harder to remember what benefits are bundled with some other product or service you've already purchased.

As a public service for business travelers facing the usual raft of daunting holiday bills, allow me to detail at least five key travel services you probably already have in your dossier. Before you spend another dime on anything, spend a few minutes with me rifling through your insurance policies and credit card benefits. You'll be surprised at what we find.

The costliest extra in travel? The various (at least four) types of pseudo-insurance that car-rental companies peddle at the counter. Not only are the waivers and supplements laced with loopholes and difficult to decipher — Hertz.com devotes 4,800 words to its optional packages— prices are obscene. The most common upsell (collision damage waiver) can cost $25 a rental day, the equivalent of an annualized premium of more than $9,100.

Ignore the hard-sell tactics at the rental counter because you're most likely protected for most eventualities by your personal car insurance. If your policy doesn't have rental coverage, you can easily add it and the annual premium could be as little as $50. One notable caveat: personal car insurance doesn't cover rentals for business purposes, so check with your employer to fully understand how they insure your business rentals.

Your second line of car rental defense? The credit card you use to pay for the rental. Many Visa, MasterCard and American Express cards have what is called "secondary" or "supplemental" coverage. It kicks in when other insurance options are exhausted. And several cards are bundled with "primary" coverage, which means you can decline all the costly car rental waivers and bypass your own insurance, too. Diners Club has been the traditional favorite of savvy business travelers because it offers primary cover of rental cars valued up to $50,000. Two Chase cards affiliated with United Airlines also offer primary rental coverage. And Chase's Sapphire Preferred card last month added primary car rental coverage.

Third-party firms now sell entire suites of products that claim to protect you when things go awry on the road: trip-cancellation coverage, lost-baggage reimbursement, lost-ticket replacement and even purchase protection and warranty extension for annoyances like cracked smartphone screens and wonky connection ports. Prices for these kinds of services range from a few dollars a month to $100 or more on a single-trip basis.

Before we discuss why you probably don't need to buy extra coverage, you should know what the insurance industry calls this stuff. The term is "junk insurance." We can only imagine what insurers think of the people who buy it.

Which doesn't mean that the coverage has no value. If your travel goes pear-shaped, it can reimburse you for thousands of dollars of unexpected out-of-pocket expenses. First stop in finding these perks free is your homeowner's insurance. Odd as it may seem, you'll often find a range of travel-rated benefits included as part of your comprehensive domicile protection.

Then check your credit cards. Higher-end iterations of Master Card (called World Elite) and Visa (called Signature) offer these perks. In the case of Visa Signature cards, expect as much as $3,000 of lost-luggage reimbursement and $2,000 worth of travel delay or trip cancellation coverage. That can cover the cost of unexpected hotel stays as well as replacement clothing and toiletries. Here are the generic offerings rolled into Visa Signature and how one issuer, Wells Fargo, handles specifics. Master Card World Elite benefits are similar, but there are notable variations in terms, conditions, exclusions and coverage values. American Express' flagship travel card, Platinum, also offers an extensive range of travel benefits.

I've been an AAA member for nearly 40 years and admit I have emotional issues letting go of this paid roadside service. Besides, AAA membership has another benefit: discounts at major hotel chains. The discount is sometimes small (5 percent), but it's much more substantial (upwards of 20 percent off standard rates and free breakfast) during promotional periods. Always make sure to search for or ask about AAA rates when you book accommodations.

Still, if you're ready to chuck AAA, you'll find roadside assistance bundled free elsewhere. Some personal car insurance policies offer it standard and others include it for a small annual premium. Carmakers, especially the luxury brands, bundle extensive roadside assistance into their value-added after-sale packages.

Major card issuers also have roadside assistance bundles. Specific perks vary. Assume the more elite cards (Visa Signature, Master Card World Elite, Amex Platinum) have the most flexible range of free service when you need basic help such as flat-tire replacement, lock-out assistance or short tows. Consult the benefits guide that come with each card for specifics.

Banks are always inventing new charges to slap on travelers and one of the most insidious is the foreign-exchange fee. It kicks in whenever you charge a purchase overseas or even buy something from a U.S. merchant that uses an international bank to process payments. Fees are hefty, too, often as much as 5 percent of the total charge.

But banks are also fond of rolling back fees and presenting the fee waiver as a fantastic new benefit. So it is with forex charges. The American Express Platinum and Chase Sapphire Preferred, which offer the most travel perks among general-purpose cards, notably do not charge a foreign-exchange fee. Most credit cards tied to airline and hotel frequent travel plans also offer forex waivers. Notable exceptions: the Starwood Preferred Guest and JetBlue Airways American Express cards slap a 2.7 percent fee on international purchases while Alaska Airlines cards issued by Bank of America charge 3 percent.

After bungling the rollout of the PreCheck security bypass program, the Transportation Security Administration is hastily enlisting private industry to convince you to shell out $85 for the service.

Don't do it. There are at least three ways to get PreCheck free.

By the TSA's own admission, the best way to ensure that you receive PreCheck privileges is to have a "known traveler" number. You'll get that number as a member of Global Entry, a government program as simple and elegant as PreCheck is complex and convoluted. Global Entry members bypass customs and immigrations lines at the airport when they return to the United States and skip the paper declaration form, too. At $100 for five years including PreCheck privileges, Global Entry is a much better value than TSA's $85 standalone charge.

You also qualify for PreCheck free if you're an elite member of an airline frequent flyer program. Even if you're not an elite flyer, however, you might get PreCheck on a specific flight. Why? TSA agents routinely herd hordes of travelers to PreCheck lanes whenever it suits their bureaucratic best interests.