Easiest way to hook up ice maker to steel pipe

Ok, so my house is older (no copper). What's the easiest way to hook up an ice maker to the steel pipes? Can I just drill a hole in the supply pipe and use a saddle valve? If so, what size hole do I need to drill? On all the saddle valves I found at home depot they only mention copper pipe. I know a lot of people hate saddle valves, but I really dont' want to pay a plumber to come out and put a "T" in my existing supply line.

Yes. It can be done. You can either pre-drill a hole or remove the valve stem and drill... probably a 1/8" hole. If you pre-drill the hole you can run the valve all the way in so that the piercing point can be used to align it on the hole. Down side is that if you have a leak and can't get it to stop then you've got to replace the pipe you drilled a hole in. For a few dollars more you can take the supply line valve off under your kitchen sink, install a tee and a couple of short nipples then replace that valve and add another with the appropriate sized outlet, probably 1/4". Your usual size supply lines are 3/8" and most icemakers are smaller (all I've ever seen are 1/4").

Saddle valves are not very dependable. They usually fail sooner or later. If I had to deal with steel pipe, I'd find a good place to open the line and install a tee. The go from there with a ball valve and adapters to the supply line.

Why not tee off from the cold water shut-off under the sink or replace the shut-off with one that has a 3/8 and 1/4 outlet.

That will work too... personally, I prefer separate shut-offs

I agree with Randy. Put the tee wherever it is the most convienent for the installation, but definitely use a separate shut off valve. They are too cheap not to have the capacity to cut the ice maker off with with interfering with the sink.

The sink is on the other side of the kitchen, so "T"ing of that wouldn't work so well.

Put the tee wherever it will work the best for you.

Mine is on the other side of the kitchen too! That cheap poly tube came in a 25' roll. I just drilled a hole in the floor behind the refrigerator to run mine under the floor all the way across the kitchen.... the whole kit was only $10... I threw away the saddle valve and installed a tee and 1/2 x 1/4 supply valve.