Installing cabinets can be done with one person but two people can make it a lot easier. The second person need only be able to lift, and hold the cabinets and so on. Upper cabinets are the hardest to install as they must be held in place while the mounting screws are installed.
Starting with the upper cabinet layout, if your ceiling is dead level you may be able to use that for a level line. However, 99% of homes have some small amount of out of level condition. If you start the first cabinet at the ceiling and as you progress the ceiling slopes down even the slightest bit, you will not be able to install the rest of the cabinets flush with the bottom of the starter cabinet.
Measure down at the starter point perhaps forty inches and make a mark. Level that mark around to the end of the cabinet run. Now measure back up to the ceiling. If that 2nd measurement is less than forty inches, your ceiling is out of level. Less, if it slopes down, more if it slopes upwards. You can adjust your starting mark according to the 2nd measure to assure all the cabinets can be installed in a level condition.
You also now want to lay out the bottom cabinets as well. Floors are notoriously out of level so the same type of level lines must be established. Once the counter top heights are established you must measure from the counter top finished height to the line previously made for the bottom of the upper cabinets. These two lines must be horizontally parallel.
Generally you want about an eighteen inch space between the upper and lower cabinets. Vertically challenged persons may want the upper cabinets a little lower to enable reaching the items on the shelves and taller persons vice versa if the ceiling height allows it. It is fairly common to see full four feet high upper cabinet today in kitchens with nine foot ceilings.
Once all the level lines are located, remove all the cabinet doors making sure to mark each one for installation later on. Locate and mark all the wall studs to assist in finding them later for fastening the cabinets. If you have a helper to hold the cabinets, lift the first one into place and using 3 inch wood screws fasten the cabinet to the studs through the top and bottom of the back panel. Four screws is generally enough but if in doubt add more.
Self countersinking screws will make a neat clean appearance when done. Now lift the second cabinet into place and using two hand clamps, clamp the side rails together of the two cabinets making sure they align perfectly in and out and up and down.
Drill a small hole in one face stile into the other and using smaller screws, screw the two cabinet faces together. Drill behind the hinge to later conceal the screw with the hinge itself. Now secure the 2nd cabinet securely to the wall. Proceed along your line of upper cabinets until they are all installed.
Base cabinets have different installation methods. A small vertical frame of wood usually four inches in height is called a “Toe Kick” is used to support the lower base cabinets. This base frame is leveled prior to the cabinets being installed. Paying close attention to the upper cabinets you want the finished product to be level and parallel to the uppers. The separation distance between the upper and lowers is not drop dead critical as long as it the same thorough out.
Once the toe kick base is installed and fastened securely, the balance of the base cabinets will rest upon the base and will also be level. Install each base cabinet fastening them to each other as well as to the wall with the same screws making sure each cabinet is level front to back as well as left to right. Once all the cabinets are in place you may wish to install your counter tops next. Doors should all be re-installed but do not tighten the screws just yet.
Many hinges allow an adjustment to the door to make the door itself perfectly level with the cabinet and some hinges allow you to adjust the door in four directions to achieve a perfect cabinet reveal on each door. Align the doors with each other as you go making sure all their bottoms align perfectly. Once done, you can drill and add the door pulls or handles.