Answer:
You should buy an ASTM approved helmet. You can buy a certain type of bicycle helmet, since ASTM helmets can be less affordable.
Make sure your helmet does not have any cracks, chips, etc. Anything that could be considered a deficiency.
The helmet must fit you. Preferably pick a helmet that can be adjusted for different head sizes, and can fit yours. When you have your helmet on your head and adjusted comfortably, shake it. If the helmet stays firmly on your head, you have fitted it well. If it wiggles or threatens to fall off, you might want to consider readjusting it.
Step-by-step explanation: