The big decision is whether to PAINT or not to PAINT. When you look at your home from across the road, does it look exhausted and dull? If so, a paint job may be THE RIGHT MOVE. It is often a very good investment and really spruces up the appearance of a home, adding valuable dollars to offers from possible homebuyers.
When choosing a color, it should not be something brash and odd, but a color that fits well in your neighborhood. Of course, the color also depends on the design of your home, too. For some reason, different shades of yellow seem to elicit the best response in homebuyers, whether it is in the trim or the basic color of the house.
As for the roof, if you know your roof leaks, repair it. If you do not repair a leaky roof, you are going to have to disclose it and the buyer will want an entire new roof. If you know your roof leaks and you don't repair it and don't disclose it, look forward to hearing from lawyers at some point in the future.
Otherwise, wait and see what the home inspector says. Why spend money unnecessarily?
The Back Yard
The back yard should be neat. If you have a pool, keep it freshly maintained and constantly cleaned. For those that have pets, be sure to always keep the area clear of "debris." If you have swing sets or anything detailed for your kids, it probably makes more sense to remove them than to leave them in place. They take up room, and you want your back yard to appear as generous as possible, especially in newer houses where the yards are not as large.
The front door & Entryway
The front door should be particularly sharp, since it is the entryway into the home. buff the door fixture so it gleams. If the door needs refinishing or repainting, make sure to get that done.
If you have a cute little plaque or shingle with your family name on it, remove it. Even if it is just on the mailbox. You can always put it up again once you move. Get a new plush doormat, too. This is something else you can take with you once you move.
Make sure the lock works easily and the key fits properly. When a homebuyer comes to visit your house the agent uses the key from the lock box to unlock the door. If there is trouble working the lock while everyone else stands around twiddle their thumbs, this sends a unenthusiastic first impression to potential homebuyers.