Keep the garbage out of sight. Make sure that it is clean, preferrably freshly painted and in excellent repair. Make sure that driveways and walkways are in good repair. Remove any stains, weeds or dirt. When possible, try to keep the driveway empty of vehicles during showing times.
Water running out of clogged eaves troughs onto a prospective purchaser is a big deterrent.
Garages are another focal point of your home. From the outside make sure that doors are clean and in good repair, preferrably with a fresh coat of paint, keep the inside as tidy and well organized as possible, clean the floors of any spills or leaks and be sure that there is enough room for people to step inside and look around - don't let it get too crowded. Touch up or paint the exterior trim. Wax, mop, steam clean, dust, scrub, paint, wash, polish, you name it. Even the spots you think no one will notice.