Draining any blister is an activity that should be done very carefully and cleanly. The best time to do this is right after a bath or shower, while your skin is still clean, soft and moist. Prepare for the lancing by sterilizing a pin or needle under a flame or in rubbing alcohol and then get some clean tissue paper ready. Sit down in a well lit area and situate yourself so that you can comfortably access the blister with both hands. Using the pin or needle, slowly and carefully penetrate the skin over the blister, use your best judgement to determine when the tip has made it into the bubble and then remove it, apply gentile pressure around the blister and inspect it for drainage. If there is none, try again. Repeat this process in solwly and carefully until you penetrate the blister and a clear liquid begins to ooze out. When this happens, cover the blister with the tissue and apply gentile pressure to the surrounding area to drain the fluid; letting the tissue absorb it.
Once your blister has been drained, you should treat it as an open wound. Dress it with a small amount of absorbent tissue or gauze and cover with a bandage. Keep it dry and clean for a couple days and if you engage in the activity that caused it in the first place before it heals, take care to provide extra padding and secure the area to prevent any rubbing that may aggrivate the wound. Change the dressing anytime it becomes moist or soiled and keep an eye out for infection.