De-clutter:
If you're not taking it with you to the next house, get rid of it.
All your ornamental stuff, nik-naks, family photos etc., pack them up now.
You want your home to look spacious.
Make a list of all the jobs that need doing and book in tradespeople to fix anything that needs fixing. This includes anything that's broken or tatty-looking. (e.g. cracked window pane, scruffy paintwork.)
Kerb-appeal starts outside. Attend to gardens, front and back, any scruffy paintwork, and make sure your front door looks smart.
Once you've done this, go round your house and take photos of every room, plus outside front and back. Look at the photos objectively. You'll be shocked at how much clutter etc you have to get rid of to make a house look good in pictures.
Price the house to sell. Do not be tempted by silly valuations from estate agents. Do not get greedy. A well-priced house that is a house that sells. Price reductions look bad.
Don't entertain buyers who are not in a position to buy. Serious proceedable buyers only.
And good luck!