Place the bra shoulder straps over your shoulders

Look at the back of your bra. Examine the long horizontal strap for the side with multiple -- usually three to four-- small brackets.

Place the cheap lingerie shoulder straps over your shoulders. Place your thumb on the left-most bracket and connect the hook on the left side of the back strap to that bracket on the right side of the back strap. Test the fit by turning your torso from right to left. Decrease the band size on your bra by unclasping the hook and attaching it to the next bracket over, just to the right of the first bracket. Test the fit again. Continue to move the clasp to the right, one hook at a time until you have a comfortable fit that's snug but not too tight.

Take off the bra and get out a fabric tape measure. Wrap it around your back and shoulder blades, just beneath your armpits and beneath your breasts in the front. Write down your chest measurement in inches on a piece of paper. Look at the tag on your bra to see if the number matches your measurement. Buy a new, smaller bra if your measurement is two or more inches lower than the number on your current bra.

Try a smaller-sized bra. It a bra is too big, the straps will fall no matter how much you adjust them. There could also be an issue with the band or the cup. If the band doesn't fit snugly, then decrease the size by one and try again. If you don't fill out the cups, reduce the size by a letter and re-try. If that doesn't work, try another style. Look for bras with a slight rubbery texture on the inside. These are meant to grip onto the shoulders and not slide.

Use clips made for bra straps to keep them in place. The clips attach the two straps together in the back so that neither one can move to the outside. If you cannot find these clips, try a large paperclip or safety pin. Lengthen the straps out to the farthest limit and insert the pin or clip to pull both of the straps together.