A seller can make their life easier if they anticipate what a buyer may or may not see as a needed repair. A pre-listing inspection or just some common sense will go a long way to help both parties (but especially sellers) reduce their stress levels in an already stress-filled process.
If anything is broken or in desperate need of repair, a seller should fix and/or replace it if they have the funds. Make sure you have all permits for additions or modifications handy. Receipts or warranties for repair work is also a plus, but not always necessary. Make sure your home is up to code with necessary mandatory repairs for a resale transaction. For instance, in California, smoke detectors and carbon monoxide detectors are required to be installed in most residential units.
Cosmetic concerns are less of an issue, but can also go a long way to facilitate a purchase. A thorough cleaning of your home and a serious de-cluttering adds value!
So take an objective look at your home, look at your budget, and see what you can afford to do before letting a potential buyer see your home. The better first impression your home will make, the better the offer you will eventually receive.