Realtors usually prescribe the following renovations as they will most likely yield profit greater than their cost:
Fix up instead of replacing. Refinishing a cabinet is cheaper than replacing it. Re-glaze bath tubs and sinks to prolong usage and save the cost of having to replace them.
Re-evaluate how you make use of space. Expanding your room may seem like a rational way to solve your space problems but you could consider getting rid of the clutter instead. You could use a physically remote storage facility to store up things you freed up.
Remodel a room for a new purpose. You can turn that guest bedroom you never use into a dining room or perhaps an office instead.
Following these simple rules you can save money and have the house you would like.