#9 or #10 are typically acceptable.

DO NOT use drywall screws.

The big box stores usually sell cabinet hanging screws in a box of 25ish. Overpriced though.

FastCap makes the best in my opinion

Screws need not be centered, but they must have enough meat to engage into. You will find that the rail holes line up with a stud in about two places in your kitchen. The rest are all slightly off, and you'll need another method at the beginning /end of some runs where there will be no stud at all.

Here is a link that might be useful: fastcap screws

Do you think these screws would work?

Their website says no predrilling required...should I drill pilot holes anyway? What size drill bit should I use

Thanks!

http://www.homedepot.com/p/GRK-Fasteners-8-x-2-1-2-in-Low-Profile-Washer-Head-Cabinet-Screw-100-per-Pack-113079/203525221?quantity=1

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Here is a link that might be useful: http://www.homedepot.com/p/GRK-Fasteners-8-x-2-1-2-in-Low-Profile-Washer-Head-Cabinet-Screw-100-per-Pack-113079/203525221?quantity=1

Is 2 1/2 inches enough to go through the rail, the drywall and at least 1 1/2 inches into the studs? I've never seen the Ikea rail so I don't know

Yes, I would drill a pilot hole - it makes it easier for you to screw the screws in.

http://www.engineershandbook.com/Tables/woodscrewpilotholes.htm

Thanks!

Do you think one screw per stud will be enough to support the suspension rail? I assume it's enough because I've never read of anyone using more than one, but do you think it would be beneficial to add an extra screw to some of the studs? It looks like it would be possible to put two screws in each stud.

here's a picture of the rail I found online
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One screw per stud is plenty.

thank you, all of you!!!. you have helped me a lot!

Related to this, how many screws per rail/cabinet? For example, if I have one 32" cabinet alone, how many screws should I be using and how many studs should I be hitting?

It's always best to follow the manufacturer's installation instructions, but you'll want a two-fastner minimum for a single cabinet. It may not always be possible to hit two studs for a single cabinet.

Ikea in store "Kitchen Cabinet Installation" literature, states screws at every stud. Once you get the part home and unbox, the pictogram instructions illustration dimension 12" on center. Typical wood frame studs are at 16" on center (do the math, studs would be at 0" & 48" for 12" O.C.) I would recommend solid blocking if you have the opportunity, other wise toggle screws should be considered.

The GRK screws pictured above are very good, although I would use (and have used) the #10 rather than the #8. The entire weight of the loaded cabinet hangs on that rail, you want a beefy screw. And the GRK screws do not need a pilot hole. You want at least 1.5 inches of the screw to be in wood, so a 2.5 inch screw works well because 0.75 inches will be taken up by the washer, rail, and drywall.

As Bray Construction mentioned, if you have the opportunity to do solid blocking before you put up drywall, it makes your life a lot easier than trying to line up studs.