1) Light. If you have windows, then don't dress them up! Keep window coverings simple so there is no blocking of light. Without windows, you'll need to rely on fixtures. Choose LED under and in-cabinet lighting for clean, white light. Be sure that your fixture globes and shades are clean, light in color, and the bulb wattage is correct. Switching to compact florescent bulbs, which are lower wattage use, often means a brighter light.
2) Color. When there's little difference between the colors of the walls, the counters, the cabinetry, and the woodwork, your eye glides over the surfaces looking for a place to rest, and that movement tricks you into thinking the space is larger than it really is. Light colors are great in a small kitchen. They reflects light, which enhances the sense of space and makes the walls seem to recede. White is the most popular color and is traditional and right for many design styles.
3) Organize. Small kitchens can have storage challenges. Counters often become storage areas, but eliminating clutter can help any space feel larger. Clear off the counters, the windowsill, and the cabinet tops, and stash as much as you can behind closed doors.
4) Use Glass. Making a small kitchen feel larger is a matter of fooling the eye and tricking the brain into thinking the space is bigger. One way to do that is to remove some cabinet doors or replace the solid fronts with glass. Adding in-cabinet lighting showcases the depth and also adds a sense of space.
5) Carve Out Storage Space. Shelves flush with the walls and recessed into space between the studs add storage without consuming valuable space in a small kitchen. If you don't have space within your kitchen, instead look for a spot near your kitchen, such as a breakfast nook or passageway, to implement recessed shelves.