All this may be presented as routine paperwork—no big deal. But the consequences of filling out forms and signing your name could be very big indeed. You might be weakening your privacy, giving up legal rights or agreeing to prices and charges you never dreamed you’d have to pay. So what should you do before taking pen in hand? When can you decline to sign? We tapped some legal professionals for their best tips.

UNDERSTAND THE PURPOSE. Knowing why someone is giving you a form to fill out can give you a better sense of how important it is and how attentive you should be. These are four categories of business paperwork you’re likely to encounter:

→ Contracts: This is a binding agreement between two parties, usually involving an exchange of value. For example, you agree to pay a monthly fee to an auto dealership that will lease you an SUV in return. Both sides’ responsibilities should be laid out in full.

→ Liability waivers: Close behind in importance, and often part of a contract, these limit or eliminate your ability to make the other party compensate you for any adverse outcomes from using its product or service.

→ Disclosure forms: Once you sign, these acknowledge you’ve received certain information (usually legally mandated), such as an adviser’s possible conflict of interest or your legal rights in particular transactions.

→ Information forms: These are requests from businesses for info about you, ostensibly to serve you better. Examples include a health assessment from a doctor or a registration card for a new product.

PREPARE TO FACE LIMITED RIGHTS. Almost every contract you sign with a major corporation will require you to give up your right to sue in court; instead, whether it’s a nursing home, car dealer or cellphone company, you’ll have to submit to nonjudicial binding arbitration. (One big exception: Mortgage lenders are prohibited from requiring arbitration.) Contracts for companies big and small will also have clauses limiting their liability.

It’s only with a small business that you have any hope of modifying a contract, says Nancy B. Rapoport, a professor at the University of Nevada, Las Vegas’ Boyd School of Law. “The more remote you are from dealing with an actual human who wrote the contract, the less likely it’s negotiable,” she says. “Apple is not going to negotiate terms and conditions with me. Pat’s Auto Repairs, maybe.”

To challenge liability limits after the fact, you’d have to go to court, where you might have to prove that the other party was guilty of gross negligence or willful misconduct. Laws vary by state.

GIVE YOURSELF TIME. A doctor’s office will often send paperwork before your appointment to fill out ahead of time. Use the opportunity to review the terms, and do the same with other contracts, Rapoport says. If you know you’ll be making a big purchase, such as an automobile, ask for a copy of the contract to review ahead of time or to take home and look over before signing. Don’t let a service representative rush you into signing a form while packing up. Take a seat and say you need time to review it. “You want to make sure you understand what you’re signing,” Rapoport says.

GET PROMISES IN WRITING. If something isn’t written in the contract, it doesn’t exist, Rapoport says. “In fancy contracts, there’s always a clause that says, ‘This represents the entire agreement between the parties,’ ” she explains. This means all the stuff the salespeople tell you ahead of time is unenforceable unless it’s in writing. Rapoport recently joined a gym and was told by the salesperson, “You can back out of it within the first 30 days.” But when she looked at the contract, it didn’t say that. This, she says, is a situation in which you should ask to have specific language added to the contract, noting that a handwritten addition to the paperwork is fine, as long as both parties initial it.

CHECK THAT A CONTRACT REFLECTS YOUR AGREEMENT. “If they’ve agreed to charge you $5,000 for roof repair, and you look at the contract and see $7,000, then you should not sign that contract,” says Ira Rhein-gold, executive director of the National Association of Consumer Advocates (NACA). “I can’t tell you how many times someone said, ‘I bought the car. I thought the interest rate was going to be 5 percent, and then I got to look at the paperwork and it was 8 percent.’ ” If you’ve received a contract ahead of time with an estimate and later are presented with the final paperwork, compare the two contracts. “Hold up the pages to each other and make sure the first line and the last line match,” Rapoport says. “If something’s different, at least you know where to look.”

DON’T SIGN WHAT YOU DON’T UNDERSTAND. If you’re stumped by the language in a document, ask for help, Rapoport says. The people who gave you the contract can’t give you legal advice, but they can explain what a passage means, she says. If you’re at a doctor’s office, ask the receptionist, who will either have an answer or can refer you to an office manager or compliance expert for further clarification, says Stephen Curley, a lawyer in Stamford, Connecticut. If there is nobody on-site to answer your questions, tell the office you don’t feel comfortable signing until staff can track the appropriate person down.

BE STINGY WITH INFORMATION. If, as part of a contract or disclosure form, you’re asked to provide information you’d rather not give out—say, your Social Security number, phone number or email address—feel free to challenge or simply ignore that. Unless a contract demands it, you likely have no legal responsibility to provide info a business or service provider wants. If on the fence, consider asking the business, “Why do you need this?” Rapoport says.

KNOW WHEN TO WALK AWAY. When should you not sign a contract? These are among the most common reasons, according to those we interviewed:

→ The terms aren’t fair and aren’t negotiable.

→ The other party won’t put into writing what was verbally agreed to.

→ The contract includes something you did not agree to or weren’t made aware of.

→ There is ambiguous terminology that you can’t get clarification on.

If something doesn’t feel right, you don’t have to sign. “Your common sense, in your experience, should dictate most of your actions,” Curley says.