I didn't bother with flowers but I did buy some nice big green plants.
I made sure there was no clothes in sight so no clothes on radiators or coats on the coat pegs, I shoved all my coats and shoes I usually had on the shoe rack (apart from a couple of nice pairs) in my car. No post left in the hall.
Got pet bowls and litter trays out of sight.
Basically no "stuff" in sight, so chucked everything from my dressing table into a bag and hid it in my car apart from a couple of nice perfume bottles.
I cleared my kitchen surfaces, so no bottles of olive oil or pans out. I even took the toaster and freestanding microwave out of the kitchen so it looked like it had more surface space. Also moved bins out.
I did buy hanging baskets, plants for either side of the door and bought a wicker door wreath as my UPVC front door's a bit ugly so wanted to give it a pop of colour and curb appeal especially since the pic of the house is usually the first you scroll past. Bright pink flowers in the hanging baskets made it stand out a bit.
Moved all of my kids toys out of his room apart from a few jelly cat teddies on his bed.
Nice pressed sheets in all rooms, I also bought satin bed runners and cushions to make it look show-homey. Nothing on bed side tables.
Outside I put all the cushions on my garden table and the parosol out (its a nice big wooden one), made the patio look bbq ready.
Tried to declutter my desk in the home office as much as humanley possible (this was the hardest) I literally just boxed it and put it in the hall when they took pictures. I was chasing that poor photographer round moving shit out of his way and checking every photo he took. I offered him plenty of teas and was polite though so he was happy enough.
I also hired someone to redo the silicon round bath as it had gotten black patches over the 10 years since it was last done and there was no hiding it. I also removed every bottle and toothbrush, leaving nothing in the bathroom apart from a mirror, a plant and a vase of pebbles. Make sure your kitchen and bathroom are as clean as possible.
I also repainted a couple of windowsills that were peeling, I didn't want them to think the windows were damp.
Good luck with the declutter OP. Xx