do away with something means discard or to get rid of something (e.g. A lot of restrictions and regulations should have been done away with years ago. It's time to do away with all of these old tax records.)

do out of means to unfairly prevent somebody, or cheat somebody out of something (e.g. She was done out of her promotion, and did Ann out of any chance of getting the job.)

do over means do something again from the beginning, or to decorate a room, or beat up, ransack (e.g. My teacher wants me to do my essay over because it is an old technology. We have a plan to do over the house next week. Many shops were done over by a street gang.)

do up means repair and improve it, or to fasten something or become fastened (e.g. Your home looks great now that it has been done up. Do your shoes up before you run.)

doze off (or drop off, nod off) means fall asleep during the day (e.g. The lecture wasn't very interesting. In fact, I nearly dozed off at my desk. Dozing off during inappropriate times such as during meals, in the middle of conversations, or even while driving.))

dress up means wear nice, special, or formal clothing (e.g. We have a dinner at a very fancy restaurant so we have to dress up.)

drive off means to leave in a car (e.g. A woman got into the car and drove off without saying anything.)
drive on (or walk on, play on) means to continue driving (e.g. We have to stop at this gas station, if we want to dive on to London today.)

drop back means move back in a position or to return to a lower level, value, price, etc. (e.g. Ann was dropped back to third place after somebody hit her car. We really don’t know why gold price drops back below $1000.)

drop by/ in/ over (or call in) means come without appointment (e.g. I will drop by/ in/ over on you for tea sometime this week. Drop by and pick up keys this afternoon.)

drop off (or doze off or nod off) means fall asleep, or take somebody and leave them, or becomes less) (e.g. The lecture wasn't very interesting. In fact, I dropped off in the middle of it. I have to drop Ann off at work before I come over. The demand for mobile phones shows no signs of dropping off.)

drop out means quit a course, stop before you have completely finished something (e.g. Ken went to university but dropped out after a year and went straight into a good job.)