I was framing out an area in my basement for some cabinets (the in stock cheapie HD or Lowes brands). Between the studs, I was considering installing a 2x6 horizontally so I can have more freedom when screwing the cabinets in. I am just wondering what if you do not land on a stud in the location you need to screw into. Questions... 1)Does this make sense? 2)Being it is only 1.5" thick dimension lumber, is this thick enough. I never installed cabinet before so have no clue how deep the screws need to go? 3)How many screws do you usually need for a 30" cabinet?

Pete--I don't know why you'd need to nail shims; they should stay in place once tapped in with a hammer. The tight fit is what holds 'em there. You could add a little wood glue, but it's not necessary. As for the cabs...YES, you need screws in top and bottom. The top cabinets should have all the support you can give them! Many times installers will add header boards across the wall to attach top cabinets. You must insure that the installation will guarantee that the mounting screws can hold the weight of the cabinets plus all the "stuff" that will be stored there. Good luck.

Holly - your response makes sense and is basically what we have here (although it is not FLUSH with the back - the back panel hangs over, which you can barely see in the picture above. But if this is true and how these are supposed to be, then why do the installation instructions say to drill pilot holes 1" from the side panels on each side. That wouldn't make it into the base at all. My husband installed it, the way gaucho advised above. It seems fine, although there is no oven in it yet. During install, we found cracks on both sides of the front (that go through from inside to outside) panels. (Attached a picture of the worst one.) I've sent pictures to the cabinet company we bought it from to see what is next. I think it should be replaced. Which mean DH has to take this one out and install again. Or they'll do nothing and we'll have cracked cabinet fronts to live with. Very annoying.

You're over thinking this. Perfectly level floors are few and far between, believe it or not, sometimes even in new housing. There will most likely, always be shims. Those "tiny pieces of wood" don't need to be any bigger, since they're flat on the ground. The strength to hold stuff lies in your cabinetry. Looks like your installer actually took serious time to make certain everything is level, which is totally necessary for your countertops!