I vote top edge for doors, centered for drawers, when placing on base units. That's a fairly classic cabinet/furniture placement of pulls/handles, and very functional, as well, for maintaining correct hinge/slide alignment.

Pull-outs work like a drawer, so I used pulls on my trash and pantry pull-out and on all drawers, knobs on doors.

Here's some info I copied & pasted below. I'm also attaching a link that may be helpful, as well. Installation: There are no set rules for placement of knobs or pulls. They may be thought of as artistic accents as well as functional pieces. Still, their placement can be crucial to the overall integration of the cabinetry plan. When placed with care a knob should blend into its context. Poorly placed knobs disrupt the aesthetic balance of an otherwise well-proportioned kitchen. Most new cabinetry is traditional in design, but sometimes in an effort to be trendy, designers try placing knobs in non-traditional places. When deciding on their placement there are some caveats that should be remembered: Cabinet Doors: Whenever possible, avoid placing knobs on a center panel. A veneered panel will not be as strong as the wood frame surrounding it. Drawer Fronts: Generally a single knob or pull is used on drawers under eighteen inches wide, while drawers over eighteen inches call for either two knobs or two pulls. Drawers over 24" wide should have two knobs/pulls to prevent the drawer from twisting when pulled. For visual continuity, pulls or knobs should be installed on false front drawer fronts as well. To position a drawer handle successfully, first determine it's visual center of mass (the absolute center od the pull). A knob's center of mass will be the mounting screw. As a general rule, If a drawer is wide enough to need two knobs/pulls, each should be centered about 1/6th of the drawer length from the edge of the drawer and positioned slightly above center. Installtion diagram for drawer handle Placement of Multiple Drawer Pulls: Length 6 = center of knob/pull Using this formula, if the the drawer is 24 inches wide, the middle of the pull should be 4 inches from the outside edge of the drawer front. In some cases it is impossible to place a handle at the optimum height because of such things as cross banding or overcrowding on a narrow upper drawer. In these instances the eye is generally forgiving. Bail handles derive more of their visual mass from the rosettes than do plate handles where the bail is recessed on a field of brass. This means a rosette handle will be placed a little lower than a plate handle whose mass is mostly a function of the backplate. The goal in all cases is to mount the handle so that the center of mass is slightly above the centerline of the drawer front. The deeper the drawer front the higher the handle should be placed above the centerline. Don't forget that the thickness of the door or drawer must be considered when ordering screws to make certain that the proper length screw is purchased. In replacing a pull, the old one should be used to measure the new one. Remember to measure from the center to center of each screw (not the length of the pull) to determine the size pull needed. If the old holes will be patched, or if a backplate will be used, size will be flexible; but don't forget that the holes go all the way through, so that the plate it won't cover them on the inside. If this matters, a second plate may be needed. It's always best to leave hardware installation to professionals who will accept responsibility for their alignment. These experts use special jigs to assure a proper match across the cabinets, which is extremely important visually. A cabinet can only be drilled once and it must be perfect the first time; if a hole is drilled wrong, the only way to repair it is to cover the hole with a backplate and start over. But that means that every other cabinet in the kitchen will require a matching backplate. And don't forget that once drilled, the cabinet cannot be returned. Here is a link that might be useful: General Rules and Guidelines

Mileady - I have the same situation you do with trim on the door, knobs, and bin pulls. One idea I don't mind is to put the knob in the middle. The other I'm tossing around is to buy two handles that go with my other hardware - one for a horizontal cabinet with a hydraulic hinge that needs to pull "up" and one for the trash pull out. I also have a cookbook shelf turned to the side on the end of a run of cabinets, which means there is a false door on the front. Of course that door needs a pull of some sort, but I keep imagining someone coming over and yanking on it thinking it's functional.