First of all, understand that our job is to determine what the value of the house is "as empty", meaning that we don't particularly care how your furniture is arranged, or the quality of your artwork. However, that being said, we are human and likely prone to making some subconscious interpretations about how well the house has been maintained. I will see a neat and tidy house and on some level automatically assume that the owners care about the property and have done the necessary work to maintain it. (This is not what I assume with a "flip" property, but more on that in another post.) Conversely, when I see a house with an overgrown yard, or with trash in the yard, rooms and garages piled high with decades of misc "stuff", I have to assume that if it is too much trouble to trim the bushes annually it is probably too much trouble to deal with a dripping noise in a wall somewhere. So the bottom line is, a cleaner, neater house will never hurt you.
At the same time, don't go overboard getting ready for an appraisal inspection. You don't need to put on a new roof, or paint the house, spend $10k on landscaping, or even steam the carpet because the appraiser is coming.
We will usually take photos of the front and back of the house, the kitchen, living areas, baths, and a representative bedroom or two. So make the bed, put your more personal items away (the things people leave on bathroom counters and headboards when strangers are visiting never ceases to amaze me), shove misc clothes and boxes into the closet, and put the dishes and food away in the kitchen.
Other things to do?