For general non-commercial use in the US, photos taken of people in a truly public place are typically usable without a model release, because there is usually no expectation of privacy there. That’s why posting on a personal blog is often different from using the image in advertising.

A model release becomes important when you want commercial use, stock licensing, or publication with buyers/editors who require proof of permission. A verbal agreement may exist, but written permission is far easier to prove.

A practical release should clearly state the agreement and include enough information to identify both photographer and subject, plus the subject’s signature or other mark. In many places, a name and signature may be the legal minimum, but that may not satisfy agencies or publishers, who often want more complete identification.

Standard stock-agency release forms are a good starting point; Shutterstock and iStock have commonly used examples.

One big caution: a mall or shopping center is usually private property, even if the public can enter. Different rules may apply there.

Because laws vary by jurisdiction, get local legal advice if you plan to rely on the images commercially.