I'd be an avid watcher of house selling programs and the main tips seems to be
a) neutral colours, no patterned wallpaper if possible
b) a bed in every bedroom and a double if it can fit properly
c) no clutter, pack away personal items if they over power a room
d) no animal smells and no cats having the run of the house
e) a table in the kitchen if there is room
f) if possible have a fire burning for viewings
g) tidy garden and tiday neighbours garden
h) do minor repairs, no doors sticking, faulty handles, broken cupboard doors or cracks in ceilings
i) make sure any good local amenities nearby are highlighted
j) clean bathrooms and ensuites, new taps, showerheads if necessary
k) make the most of your storage space (make sure there is storage space) don't have your wardrobes crammed with clothes as it looks like there isn't enough space.
l) no stained or dodgy looking carpet around toilet bowls (these must also be spotless)
m) nice smell in the house, apparently coffee/fresh bread smell in the kitchen isn't a myth
n) if the back garden can be seen from the kitchen don't have it obscured by anything
o) no dirty clothes waiting to be washed in utility room or kitchen, and no clothes hanging on the line
There are many many more things that can be done but these are the ones that don't cost any money, only look at spending money if your house hasn't sold within a reasonable time period and all the other boxes are ticked. Thats when you start laying new floors, replacing bathroom suites etc.