Warning signs for brakes.
Here in New Hampshire, we have annual State Inspection. For many people this is when they find out that their brakes are beyond NH state inspection limits. Sometimes this comes as an unpleasant surprise and unexpected expense.
Brakes are wearing items and do wear out. There are some things we can do to better plan for the day we need brakes.
If you have your vehicle serviced at Accomplished Auto at 134 Hall St Ste A, Concord NH 03301 603-226-6630. Part of every service includes inspecting rotors, and measuring brake pads for wear. 
We document it in your digital inspection. This way you can track pad wear and will get a heads up when you are getting close to the state inspection limit. Another advantage of doing this is that we often can find signs of uneven wear, rusted rotors, and stuck brakes. When addressed early can extend the life of your brakes as well as keeping you safe on the road.
If you are not doing this there are a few other things you can look for.
Noises such as brakes grinding, brakes squealing, and rubbing noises all are indications that you have brake issues. Many manufacturers include warning devices that cause squealing noises before pads completely unsafe. Some even include a warning light on the dash. If these things happen you should immediately contact Accomplished Auto Concord NH 603-226-6630.
If you have brake pulsation or brake vibration when braking especially from highway speeds. Excessive brake dust on the wheels can also be a sign of accelerated wear. Any of these warrant a brake inspection.
If you have increased brake pedal effort. Or spongy brake pedal. These are signs of serious issues that should be immediately addressed.
Last thing is on many cars, especially with alloy wheels, you can inspect the brake rotors through the wheel spokes. They should be clean, smooth bare metal color on the brake rotor face where the brake pads touch. If there is lots of rust on the brake rotor. The pads are not applying even pressure on the rotors and need to be inspected. If the brake rotors have grooves or have rough metal on them have them inspected.