Do any of you have any tips on the best hardware and methods for mounting a fluorescent fixture to the ceiling?  For instance, what size wood screw is usually best?  What do you use if there is no joist, a toggle bolt?  Is it a good idea to drill pilot holes first?

With a joist, a few 1.5" - 2" wood screws work fine. Without a joist, toggle bolts.

I've used no 8 molly screws in dry wall without any issues.

i dot recomment attaching anything to drywall ceilings. I had my share with a 2x36w T8 fixture nearly faling down when the ceiling got wet

If you mean the plasterboard (gypsum filled between two sheets of a carton paper), you have to find the metal support beams (used to support the board) and attach all loads to these.
Otherwise the plasterboard itself could support only a small frame-less picture or so.

In any case I would be very careful about the weight of the fixture - here the lightweight construction of modern electronic ballasted fixtures come handy, but you have to accept their lifetime being shorter than the old, heavy magnetic ballasted fixtures.

And if it get moist, it does not support even it's own weight, so it should be kept all the time dry anyway...

Fixtures are commonly mounted with 2-3 2" #8 or #10 wood screws with a washer screwed directly into the joist. You might have to drill a hole or two in the body though. If mounting over a junction box I usually drill two holes next to the large centre KO so the light can screw on the box for added support.

Toggle bolts do work but you should make sure at least 1 screw is in solid wood.

Metal framing is very rare in NA residential construction as is concrete.

If mounting on a drop ceiling, there are metal clips that clip on the main T-bar that are typically used.

I said metal frames, because this is the virtually only type used here, although I know the wood framing is quite common in the world as well.
In any case the panels need some support structure, the point is to attach the fixtures to that support structure and not only to the panels, as the panels usually do not have enough structural strength...

Well, seeing as Patrick is based in NA I really don't think metal framing would really apply in his situation and I think it's evident to everyone that ceilings panel require a frame to support it...

In Italy, 99% of houses are built with bricks, so we use wall plugs.
Actually, 5mm or 6mm are the best choices because strenghtness.

I still haven't gotten around to installing these fixtures and I was taking another look at it.  I'm still unsure the best way to attach them and whether or not mounting them over an electrical box is one of the intended configurations.  I thought the big knockout might be for that purpose.  However, it is only 2" compared to the 4" of the box and the fixture is only a little over 3" in width.  That's not wide enough to completely cover the box.  I asked two different people at the big box store, and both recommended not putting the fixture directly over a box.  However, neither could tell me the intended purpose of the 2" KO.  I was thinking maybe a cover like this would work, but I'm not sure.  Any ideas?

Here most ceilings are cast concrete. Wiring is done in flexible plastic pipes and plastic connection boxes network installed in the concrete forms before casting in the concrete. into them conductors are pulled with fish tape after the building is up

The way i consider proper for making the lamp termination in the ceiling is putting in there a connection box with just the 1 input wiring pipe entering it, so the lantern can be installed over the box. Or if the lighting circuit serves other lights too, continue the pipe to the next lanterns from the same box too

Sometimes (in the good setups usually) this is exactly how it is done
In this example a lantern is installed next to the box instead of on the box - http://www.lighting-gallery.net/gallery/displayimage.php?album=2196&pos=28&pid=78485

Sometimes the builders also route to the same box pipes serving unrelated stuff like receptacles. I dont like this because the box ends up stuffed with wiring unrelated to the lantern it is supposed to serve, and you have to pull down the lantern even when you want to inspect wiring for something else....

And sometimes the builders save 0.5$ on a proper box and just leave the end of the plastic pipe itself exiting from the concrete.... Now this is bad cause there is no recessed space to tuck the connections in and they can only be made inside the lantern, and that it is not possible to close it with a plain cover if the lantern is removed
This is from my home - http://www.lighting-gallery.net/gallery/displayimage.php?album=2438&pos=25&pid=66903



With those installation methods all whats required at the back of the lantern is to be able to cover the termination (box or end of pipe) and have a hole for the incoming wires - it dos not have to match perfectly the box shape, and it is usually not mounted to the box with screws either (except for some small basic incandescent sockets, not stuff like fluorescents) so does not have to match any screw holes of the box either. The box is just left as is without cover under the lantern, the lantern closing over it

If the lantern is too thin to cover the box, sometimes the electricians instal a blank cover on the box and cut a hole for the wiring in it, then install the lantern so that it covers the hole so you see a lantern with the edge of a blank connection box cover visible under its center

So the back of the lantern somply have some cutout for convenient entry of wires, nothing special - http://www.lighting-gallery.net/gallery/displayimage.php?album=2158&pos=4&pid=83277

The mounting of the lantern which holds th actual weight is by bolts placed elsewhere in the lantern - usually 2 bolts paced farther apart near the heaviest parts of the lantern where the ballasts are. When mounting the lantern



No special suggestions, just sharing

I've installed a couple of flouro's in my garage ceiling with a large fixing called (in Australia) "Wall Mate". Its a large diameter plastic or metal hollow screw that drills itself in the plaster then a normal self tapping or plaster board screw threads into it. The wall mate has large threads that spread the load over a wider area and are hard to pull out. If you do a google search, it may be called something else in other parts of the world.

We have something similar here. In our version it is not threaded omn the outside, but you drill a hole and push it in. When you then screw the self threading screw into it, 2 wings of its sids open and hold on the internal surface of the wall

They are ok for something small but no way i'd use them for a fluorescent strip