While you certainly don't have to tackle any major projects in preparation for your appraisal, there are some things you can do to help your home appraise for top dollar:
Touch-up interior paint. This is one of the fastest, cheapest and easiest ways to spruce up your home and show that it has been well maintained and is in good condition.
Repair any peeling paint on the exterior of your home (and remove paint chips on the ground around your home), especially if your loan (or your buyer's loan) is FHA. FHA does not allow peeling paint and your closing might be delayed if you have to satisfy this stipulation and have the appraiser make a second visit.
Replace burned out light bulbs. Well lit rooms look better in the pictures that will accompany the report.
If you have made recent improvements or updates to your home, take a few minutes and make a list of those improvements with the approximate costs. This information is very helpful for appraisers and makes sure that you don't forget to mention a recent update which might affect the value of your home.
Don't spend hours deep cleaning your house before the appraisal (unless you want to). Especially for refinance appraisals. Don't stress if there are dirty dishes in the sink or unfolded laundry in the laundry basket. Or toys spread around the house. Appraisers aren't there to rate your housekeeping and having a "lived in" house doesn't effect the value.
Don't be surprised when the appraiser starts opening closet doors or shed doors. We don't want to miss a key feature of your home and many lenders require detailed images of the interior of your home and any out buildings.
Don't be offended or upset if the appraiser won't tell you a value or value range on the spot. Many hours go into developing the opinion of value for each property and appraisers aren't allowed to discuss value or "guess" at a property's value. We are happy to answer questions about how the appraisal is done, but we cannot discuss the value.