Most folks won't spend more than 3 seconds looking at a business card; you probably want to make sure that either your URL or phone number is easy to see (i.e. design for lazy users).

I would disagree about "no more than two colors" unless cost is a prohibiting factor. Depending on your logo and layout you may need more than that (or your logo may not fly without it).

I usually use Illustrator to do the layout (because vector graphics scale better) but there's nothing wrong with using Photoshop. You're going to want to find out what the text area and bleed area for your printer are; they can usually supply you with these numbers.

If your biggest concern for material is getting them through airport security, then you probably don't want metal. If, however, your biggest concern is getting clients to call / email you (which is the point of a business card) then don't immediately dismiss metal (or any other material). There are tons of sites that showcase creative business cards printed on suitably amusing materials (wood, paper, metal, plastic, etc.). The idea is that your card should stand out from everyone else's.

Raster images should be 300 dpi and not overly scaled to prevent jaggies (jagged edges caused by aliasing and low resolution scaling). Most printers want CMYK for 4-color printing, so you may have to find a way to convert your raster image to CMYK. And for god's sake, don't use Comic Sans or MS clipart.