There are several simple, low-cost things you can do to boost the value of your home. These include eliminating clutter, washing windows, installing higher wattage bulbs to create a brighter environment & possibly a new coat of interior paint.
Larger projects, like adding bedrooms and renovating kitchens and bathrooms, typically yield more substantial increases in sales price. But these projects are not always an option when it comes time to sell, as they need more planning ahead of time.
It is also very important to get certain inspections & repairs done PRIOR to putting your home on the market. Your agent can direct you which inspection types to have done & which repairs to have performed that will take the negotiating power away from the buyer. Remember, if you see items needing repairs a buyer will too & the buyer will only magnify those issues during negotiations.
Depending on the market, staging your home may help to paint a picture for how buyers will use their new space, can also add value.