1. "Ensure that when you pop your hand behind your back and slip your thumb under the hooks [or band, if it's not a bra strap style] that you can only pull it out by half an inch with some resistance."
2. "Sports bras often cut high on the chest to contain the tissue. Run your fingers inside the top of the cup to ensure there's not an air gap in the cup, where there would be free movement if you were exercising."
3. "Take a moment in the changing room to jump on the spot and check you're happy with the level of support. Ask a staff member to adjust your shoulder straps [do this yourself at home occasionally, as hardware will slip over time due to exercise]. If you're still not comfortable try on more sizes and keep testing—don't expect to take your typical size."
5. "Try and purchase sports bras that are adjustable, with a bra strap fitting. Pulling them over your head stretches the elastic more quickly, and when it stretches, you won't have the option to make it smaller."