Band
The underband provides a huge 80% of the support you receive from your bra. That's why it's so important to check how your underband feels on the loosest hook, as this should feel firm but comfortable.
Back
The back of your bra should be in-line with the front and fastened on the loosest hook. When the elasticity of your bra naturally stretches over time, your look may be fastened on a tighter hook.
Cup Height
Make sure the cups of your bra aren't too high under your arms. This may cause rubbing or discomfort during wear.
Cup Fill
Nobody likes likes a cup half empty, right? The whole of your breast should fit neatly inside the cup, with no empty spaces and no excess spilling over.
Wire
Make sure you're wired up correctly! The wiring of your bra should sit flat against your chest and around the contour of your bust. Wires and boning must lie flat against the body and right around the contour of the breast.
Centre-Front
The centre-front of your bra (between both cups) should sit flat against your chest when fully secured and supporting your breasts correctly.
Straps
And finally, adjust the straps. The straps should feel firm but comfortable. If they can fall off your shoulders, they may need tightening, or the bra could just be too large for your breast size. if you find these are leaving red marks and digging in, the bra may be too small.