Making Curb Appeal Happen:
WASH EVERYTHING!!!! windows, front door, porch and garage doors. Rent or buy a pressure washer to get rid of grime on the sidewalks, walkways, siding etc.
Remember you have been living in this house and you have been putting up with this stuff because of time, energy and perhaps budget. Realize that some of this fixing is just a nuisance however to the buyer they see it as a BIG PROBLEM and will automatically deduct massive dollar amounts from the purchase price when perhaps all it takes is a little elbow grease and time.