Step 1 - Connect the clasps or bra hooks together and remove brassiere padding. Separate colored undergarments from whites.
Step 2 - Get a mesh bag or a lingerie bag and place all the undergarments inside. I've also heard of a bra ball, a type of round/sphere plastic contraption which can hold up to three brassieres without ever worrying of misshaping your bra after washing.
Step 3 - Use lingerie friendly detergent powder or a detergent for delicate fabrics.
Step 4 - Use cold or warm water and set the machine in the gentle or delicate cycle.
Step 5 - Once rinsing is done, remove the excess water by laying all the undergarments (except the brassieres) on a towel and rolling it up with the garments inside. Do not wring your undergarments. Just do a gentle squeeze on your brassieres to get rid of the excess water. Hang and air dry all your undergarments. Avoid using dyers to keep the pieces from shrinking and the colors from fading. Using the dryer might also ruin your undergarment fabric. If you really want to use the dryer, place it on a low or medium setting.