You should remove all cabinet doors, all drawer fronts, and the hardware too. Save those hinges if you're going to use them later on. Next you need to sand all the end panels and cabinet boxes. Only use your hand to sand down these parts, or you will go too deeply into the wood. Clean up the surface getting the dust off, and wash it with some soapy water.
Next to resurface kitchen cabinets you should begin with those end panels, place wood glue on them. Place on the new panel and get the glue that has come out when you've pressed it down. Put nails in the panel to hold in place.
Adding your veneer should be your next step. Cut these pieces with either scissors or a knife, they should measure half an inch wider and be two inches longer than what your covering. Place it down after you've removed the backing and press down firmly. After your done trim off the extra veneer with your knife.
Only do one cabinet at a time so you don't get confused as to what step your own. Sand down the edges of the veneer with your sandpaper. Now you need to place up the hardware. Whether you're using the old hardware or new stuff.
If these don't fit the same holes as before, fill those other holes with the wood putty. Now in your resurface kitchen cabinets project your ready to place up and start replacing kitchen cabinet doors and drawer fronts again. Maybe even consider adding in some cabinet drawer slides to make organizing easier.
So how do you want to redo those doors? You can match them with what you've done to the base, or be more creative.
Another great article you should read - What is the Cost of Kitchen Cabinets?