The kitchen is the operational hub in most homes - integrate it seamlessly with the surrounding areas to maximize connectivity.  Hide a pantry behind a pocket door and accentuate your backsplash with under cabinet lighting.  Ensure there is plenty of cabinetry to house all of the chef's tools.   

Bathrooms in older homes tend to be smaller than you wish and lacking in natural light.  Well designed vanities and more efficient use of existing closets can go a long way in making them feel larger.  Bright accent pieces and tile provide modern touches.