Quoted:
glass should be a very clean cut which will heal quickly if treated properly.

First, recognize if you need professional medical attention.  If the cut went completely through the skin, if anything underneath the skin is cut, or any major blood vessels are cut, get medical attention now.

Otherwise, you want to use butterflies, steri-strips, or similar products to pull the edges of the wound tightly together.  You want a clean wound as much as possible, do not use anything on it other than some saline to flush it out if needed or betadine for antiseptic.  Go all along the length of the cut.  You may need to put direct pressure on the wound for a few minutes to reduce the bleeding enough to be able to do this.  Once you get the sides of the wound all pulled together there should be little remaining bleeding, cover with a bandage to keep it clean and moist to allow it to heal.  Change the bandage if it gets blood soaked or wet, and put a new bandage on.  Do not let the wound dry, "air out" or scab over... keep it covered and moist to fastest healing and minimal scarring.