What I do is walk around the house trying to have new eyes (very hard if it's your house, but it can be done) and say to myself "What is the story I am trying to sell here? Who is most likely to buy it, and what will appeal to their vanity?"
Then I strip out all the personal stuff, finish outstanding DIY jobs (most important of all), spring clean the place, move out anything that is not beautiful or immediately useful, and then the fun starts with the props.
In the living room - How would they watch TV? How would they spend their leisure time? Could they have friends around for drinks in there? I would have fresh flowers, glossy magazines and holiday brochures that said "Affluent family".
In the dining room - What would Sunday lunch be like in here? What would dinner parties look like? I would set the table and make it look like a magazine setting, with a low flowers arrangement in the centre of the table, which should seat 4 or 6. The story here would be "Fun and generous host".
In the master bedroom - How elegant is this? How relaxing? How good would the nookie be in here? Is there a restful, stylish atmosphere? I would hang up a designer frock on a padded hanger somewhere obvious and discreet at the same time, dress the bed well with lots of pillows, a nice throw and matching cushions, have a few of the latest hardback books by the bed and make sure it smelt subtly inviting (eg vanilla, rose, narcissi). The story here is "Happily married couple who still have a bit of night time action". Put a stylish picture of yourselves as a couple on one of the bedside tables or the (mainly clear apart from Chanel perfume and a couple of upmarket ornaments) dressing table.
In the nursery - How broody can this make people feel? Lose the plastic toys and make it somewhere that says "Peaceful, happy, designer baby".
Other bedrooms - Put a double bed in if you can, with space either side to walk past. In a single bedroom you can put extendible Atlas beds from IKEA and have them at 3/4 length to create the impression of extra space. Again, dress beds nicely so Goldilocks would want to get in. If the bedroom is really tiny, consider putting in a futon and giving it an Oriental theme with lovely lighting through rice paper lamps. For a double bedroom, you should always have matching bedside tables and lamps to balance the eye.
In the kitchen - Does this tempt you to try new recipes? Get the oven/hob/extractor fan professionally cleaned by Ovenu. Get rid of all your everyday stuff, and then go to Waitrose and buy groceries purely on the basis of their looks - upmarket bottles of balsamic vinegar, olive oil, Dijon mustard, expensive pasta in jars, biscotti, amaretti, that kind of thing. Have stainless steel accessories - get these from the pound shop if you can, and buy a stainless steel kettle and toaster. Keep a fruit bowl filled with attractive, exotic fruit. Replace the doors or paint them cream with special kitchen door paint and add new handles. Paint tiles cream if necessary and apply tasteful tile transfers to break up the monotony. Put out designer cookbooks in a little pile as if you are about to use them. The story here is "Delicious cooking and sophisticated treats".
In the bathroom - This should be spotless. If your suite isn't white, have towels in the same colour as the fittings and paint the walls cream. Clear away all your toiletries and buy designer ones from beauticians, hairdressers and so on, and put these out instead. Have brand new soaps by the sink, and consider putting in a new toilet seat. The story here is "Sophisticated spa".
In the garden - Make sure you have a nice green lawn, and also somewhere to sit out and eat - consider buying a wooden table and four chairs. If you are short of plants, consider having three or four large terracotta pots and filling them with winter flowering pansies or other seasonal plants, positioning them where you would like to draw the eye.
Warning - once you have done all this, you won't actually want to move ...