Internal
Declutter - Get rid of excess furniture and ornaments. Rooms will look more spacious. Tidy any trailing wires etc.
Too many family photos? Store them away.
Carpets and Floors - Vacuumed /Washed.
Bathrooms - Toilets Sinks Showers etc must sparkle. Get rid of mildewed Shower curtains. Shampoo bottles etc - store tidily in press. Hang your luxury towels. Bowls of Pot Pourri are a nice touch.
Bedrooms - Beds made and rooms tidy. - Absolutely no clothes or shoes thrown around. Children's' Bedroom - toys can be stored neatly in a coloured box.
Kitchen - all appliances spotless. Worktops clutter free. Walls may benefit from a paint job.
Spare Room - if you have a spare room full of junk, empty it out. It will offer more appeal as another bedroom or study.
Paint jobs - if you feel that a room would look better with a fresh coat of paint stick to a neutral colour.