This was me two years ago!
Try and think about your house as a stranger would, or see if you can get an honest opinion from a friend. Ours was quite full, probably looked 'cluttered'. We put two armchairs, two wardrobes, several bookcases and their contents and a load of hobby stuff into storage to make it look more spacious. You want it to look like storage isn't a problem.
Use that opportunity to declutter anything you no longer need or want and get rid of it via charity shop, tip etc.
Clean everything really thoroughly. We repainted dingy bits where corners had got chipped or where the stairgate had been.
Clear up outside - what does it look like as a drive by? Keep leaves swept up and grass cut.
Get your paperwork together - FENSA certificates, guarantees for work done on the house, research local solicitors and decide which one you want to use.