Not every home improvement is a great investment:
Adding a pool in a neighborhood with few pools is not always a good investment decision, especially if the pool takes up most of the yard... I've had numerous buyers decline a house they loved because it had a pool and very little yard.
If you have a four bedroom home in a development where your home is the largest, a fifth bedroom may bring diminishing returns. Unless it is set up as a separate suite to be used as a "granny flat", as extended family housing is currently in demand.
Keeping up with maintenance and repairs is THE most important way to add value to a property...including the gardens. Lawns are out these days, due to the water shortage and, the cost of water now and in the future.
Typical returns on remodeling projects:
Kitchen: 70-75%. Limit spending to 20% of the home's value
Bathroom: 80%. Large showers are currently very popular, spa tubs are out.
Window Replacements: 75% in addition to energy savings
Low-care landscaping, built-in BBQ, gathering area 75+%
Talk to a good Realtor about improvements that are currently in demand and what your project would add to the value of your property.
Remember the 3-C's: Color, Clean, Clutter
Don't use trendy colors in carpeting, tile or flooring, especially bold colors. Keeping colors in neutral and earth-tones keeps a house up-to-date and fresh looking. Stay on top of maintenance and details. Don't let clutter accumulate anywhere on the property...less is more!
When in doubt, call your favorite Realtor for advice. We know what sells, what detracts, and what would make your home improvements add value; in addition to adding ownership enjoyment!
(some information from Angie's List, CAR and personal experience)