People will start making judgments about your property before they've even stepped through the door.
So even if it's perfect inside, a messy front garden, peeling paint on the front door or clutter in the hallway could have them mentally knocking down the amount they're prepared to offer.
"Kerb appeal is key. A tired or neglected entrance can create a negative impression before a buyer has even set foot inside your home," Helen said.
"A weekend spent undertaking relatively simple jobs like repainting the front door, cleaning the windows and tidying the front garden will be time well spent."
Mistake two: Covering up period features
If your home has original features such as fireplaces or wooden flooring, they might not be to your taste. But they will add value to your home so it's worth restoring them before you try to sell.
"Try to work with the existing style and character of your home rather than against it," Helen said.
"Original period features will usually add value so considering retaining and restoring them where possible.
"Take inspiration from what's already there. Features that look great in a modern home can sometimes look out of place in a Victorian or Edwardian house (and vice versa).
Mistake three: Neglecting simple DIY jobs
"While homebuyers won't necessarily expect everything in your home to be perfect they will be reassured by signs that the house has generally been well cared for and regularly maintained," Helen said.
"Tick off all those little jobs you've been meaning to get round to, like replacing that mouldy grout in the bathroom."
Mistake five: Cluttered rooms
Clutter is the biggest enemy when it comes to impressing potential buyers, even though they logically know it will all be gone by the time they move in.
"Prospective buyers need to be able to quickly assess the potential of a space and visualise how they might live in it and put their own stamp on it," Helen explained.
"It's much more difficult to do this if a room is filled with bulky oversized furniture or too many personal belongings.
“Hide excess clutter in the loft, or rent a temporary storage unit.”