The numbers to know

From the operating rules in 14 CFR part 107, subpart B:

Limit	Rule	Section
Altitude	400 ft above ground, or within 400 ft of a structure and no more than 400 ft above its top	107.51(b)
Speed	87 knots (100 mph) groundspeed	107.51(a)
Visibility	At least 3 statute miles from the control station	107.51(c)
Clouds	500 ft below, 2,000 ft horizontally	107.51(d)
Night	Anti-collision lights visible for 3 statute miles	107.29
Line of sight	The remote pilot, the visual observer or the person at the controls must be able to see the drone for the whole flight	107.31
Right of way	Yield to all aircraft	107.37
Controlled airspace	Class B, C, D and Class E surface areas at airports need prior ATC authorization	107.41
Over people	Not over people unless they take part, are under a covered structure or in a stationary vehicle, or the operation meets a category in subpart D	107.39
Alcohol and drugs	The manned-aviation rules in 14 CFR 91.17 and 91.19 apply	107.27

Before each flight

Section 107.49 makes the remote pilot assess the operating environment, including risks to people and property nearby, before flying. In practice that means checking the airspace, the weather against the visibility and cloud limits, and the drone and its battery.

Registration and Remote ID

Every drone flown under Part 107 must be registered: $5 per drone for three years, and the registration number must be on the drone before it flies (FAA).
Registered drones must comply with Remote ID by one of three ways: a standard Remote ID drone, a broadcast module, or flying inside an FAA-Recognized Identification Area (FAA Remote ID). See Remote ID.

What Part 107 does not allow by default

Flying beyond visual line of sight needs an FAA waiver under Part 107. Pre-programmed mapping flights still have to meet every limit above, including line of sight. The coming Part 108 is meant to make routine BVLOS possible without a waiver (status).

Plan a flight inside the limits

A mapping mission at 120 m (about 394 ft) sits just under the 400 ft ceiling. The ground sample distance planner warns you above 120 m and gives the photo count and time in the air.

Quick self-test

Away from structures, 400 ft; groundspeed, 87 knots; visibility, 3 statute miles; clouds, 500 ft below and 2,000 ft horizontally. If any of those took a second to recall, the practice quiz covers them, and the licence page covers getting the certificate.