Simple stuff:

Trim or remove any shrubs that cover part of the front of the house
Mulch flowerbeds and put in a few hardy plants
Pay particular attention to the front door and front porch. Clean/paint both. Often, you may find that replacing a front door makes sense.
Cleaning, of course
Paint interior rooms to neutral colors
Replace/repair anything that is obviously broken
Get as much light into the house as possible. That may mean discarding old blinds, etc.
Consider updating cabinet pulls (unless the existing ones are "collectibles," as opposed to just plain old)
Replace kitchen and bath faucets, unless they can be cleaned to sparkle
Remove worn/stained carpet if floors underneath are hardwood (this can be a positive selling point, even if the hardwood floors are not sanded and refinished)

Great - those things I can do.

Susan-you keep waffling back and forth.

Have an EXPERT BROKER in your area give 3 values.

Full repair,as-is,and flip. Then decide on which one you want to do.

Greed is a wonderful thing.Sellers always hope a little polish will bring them in much more in return but often it bites them in the butt.

The "flip" value is going to be at least 25% below the AS IS, but that percentage will vary a great deal depending on the base value of the house. The flipper needs at least that margin between the fully-repaired value and the AS IS value, or there is no profit left for the flipper. You must realize, also, that the flipper needs to cover real estate commissions and the holding cost of the property while it is on market.

Price paid + labor cost of renovating + material costs to renovate + commission and/or cost of marketing the property + interest on investment during marketing + insurance and utility costs = a flipper's investment. Now add some profit into the equasion and you see things from the flipper's point of view.

On a side note, even most experienced agents cannot accurately predict a flip value. . .

In addition to what Lizl says there is the cost to hold. This is interest expense and property taxes, utilities and so forth. The longer it takes to complete a project, the more it cuts into potential profits.

There's a flipper in my area that used to be able to turn a pig into a sow's ear, and have it sold in 30 days from when he closed on his purchase. He had it down to a science, with an entire company built around buying and reselling properties. The change in subprime lending requirements has made him rethink his procedures, however.