The kitchen needs to be uber clean from top to bottom.
If you have plant shelves, remove all greenery and accessories. These items are not necessary and will detract from the height of the ceiling. (They also collect dust.)
If your kitchen has wallpaper and borders, remove them and paint the room an appealing neutral color.
If your countertops have seen better days, consider updating them to maximize appeal.
Lighting sets the mood for a kitchen. Be sure there is lots of natural light flowing into the room.
Pack away all small appliances that you do not use daily.
Organize the pantry and make it look spacious.
If you kitchen looks too monochromatic, consider bringing in color with a few accessories such as a bowl of apples or lemons. A cookbook on a stand looks lovely especially when the page is turned to one with a beautiful photo. If you have an eat-in area, set the table with layered dishes, glassware and napkins.