How your house looks invites buyer interes and speeds the sale process. Overdoing the fix-it's is a money loser ... So, be smart about what you do. Think of it as a part of "house staging" which goes deeper. There is also a tax difference between a repair and a "betterment." The latter is included in the basis of the house ... thus reducing your tax liability ... just don't get carried away.
Start buy doing some tours of competing houses for sale. Carefully note the upgrades, deficiencies, significant add-ons ... This is your competition if you want top dollar. How does your house measure up to the competition? Consider their asking price ... do you have the dog on the block which could be made competitive at a much higher opening bid?
Lets start with repairs ... Problems with the house which would diminish the buyer appeal should be fixed. Drywall cracks due to typical sagging? Fix. Broken/cracked driveway or walkway? Fix ... but unless the area supports it, upgrading to interlocking pavers might not be recoverable. Plumbing leaks? Fix, particularly the main, the pressure regulator, run-on toilets, dripping showers ... Check garbage disposal for leaks/functionality ... same goes for dishwasher. Change out faucets? Probably not, unlesss yours are rusted and pitted. Eradicate any surface mold with careful use of bleach or special purpose remover BEFORE the real estate agent does his initial assessment. If he sees "MOLD" he may require you to disclose what is not truly a problem.
Dated electrical fixtures? Leave, unless all the competing houses have all dumped the 1980's brass fixtures ... Replace with LED bulbs? No, you will get zero payback for "green." Add security lighting outside? Maybe ... depends on the competition and how handy you are at adding such fixtures.
Carpet/flooring? Expensive items which may or may not get any return but could speed the sale (possibly bidding war). You have to compare your place against the other housese for sale. Laminate is popular now and easy to install. However, most will tell you you cannot get your money back, even if you DIY.
Interior paint? Invest in neutral colors, removing your custom lime green touches or left overs from the "Southwest Look." Make sure all traces of grease, grime and wear are covered. Pay attention to window sills ... use semi-gloss, not flat paint. Check for mildew or mold in the windows ... wipe it out!
Exterior? Investing in a major landscaping overhaul is a loser. However, a serious cleanup, hedge trim, lawn rejuvenation, and spot color planting for the Spring is a good idea.
BEST OF LUCK ... and bring your before-and-after pics back to this site ... we love to make fun of newbies!