Read the whole paper before you sign, don't sign for others, and don't sign a blank page

High value
Evidence A
Saves money
Free
Takes minutes
Some willpower

In plain words

Once you sign, it counts. A fingerprint counts the same as a signature. "I didn't read it carefully" or "I thought it was something else" will mostly not hold up in court. So take a few extra minutes to read from start to finish, ask on the spot about anything you don't understand, and take a photo for your records. Don't sign for anyone else, don't sign a blank page, and write the purpose on any copy of your ID card. Electronic signatures and face-scan confirmations count as signing too.

Cost: Free. It takes a few more minutes to read the contract, IOU, guarantee or hiring paperwork from start to finish. Ask about anything you don't understand on the spot, then take a photo for your records. The hard part is reading it slowly to the end while the other person is watching.
What you get: A contract formed according to law is protected by law and binds both parties who signed it. Once signed, you have to perform it fully as agreed. Civil Code (民法典) Article 490 says that when a contract is made in written form, it is formed when the parties "sign it, put their seals on it or press their fingerprints on it." Fingerprints are one of three equal methods alongside signing and sealing, and a contract is formed just the same with a fingerprint. "I didn't read it carefully" or "I thought it was something else" rarely works in court. If you don't sign, you won't take on debts and responsibilities that aren't yours (China)
Notes: "Don't sign for others, don't sign blank pages, write the purpose on ID copies" is practical experience and has no separate official document. They all serve one goal: don't let your signature be pieced into a contract that is legally valid and that you then have to honor. Electronic signatures and face-scan confirmations count as signing too. When an acquaintance asks you to help by scanning your face or signing to take out a loan, see §8.45 (help by scanning your face).
Evidence grade: A : Specific numbers from meta-analyses, large cohorts or randomized trials; for law and policy, the statute or official text.
Sources: 全国人大 (2020). 民法典（第四百六十五、四百九十、五百零九条）. https://www.spp.gov.cn/spp/fl/202006/t20200602_463888.shtml

Mentioned in

Translated from the Chinese original. Original book, section 8, tip 17. This section describes legal rules, mostly mainland China’s. It is general information, not legal advice; for your own case, talk to a lawyer. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer