Who doesn't like Process?

• I usually make my own screens. That saves money ($4 home-made vs. $10-$20), and lets me try out different types of screen cloth.
• Frame pieces are available for $2/frame or so at most art stores, or can be salvaged from old picture frames.
• A staple gun is a quick and easy way to attach the fabric (wrap the fabric around the edge of the frame and staple on the reverse side-- that seems to make it easier to pull the fabric tight..
• I use Diazo Photoemulsion. I generally let the coated screen dry overnight. Keep emulsion refrigerated when not in use (I've used it after a few months refrigerated with no problems, but have had problems after 6 months).
• For spreading the emulsion, a stiff sharp-edged squeegee works well, but for printing ink on fabric a more rounder, soft squeegee (see below) works better.
• If you're printing on t-shirts or other fabric that will be washed, be sure to use "Fabric" screen printing ink.
• After printing on fabric, let it completely dry (an hour or more), then iron 4-5 minutes on each side, at the highest temperature the fabric will allow. I've washed some of the screen printed shirts 20-30 times on the warm "colors" setting with no noticeable fading.
• Exposing the screen takes about an hour with a 100W flood lightbulb in a reflector, about 18" above the screen. The unexposed emulsion easily rinses out in warm water.
• Printing on dark t-shirts (especially black) can be tricky. The color of the shirt shows through, and most inks just won't show up on black (though you can see them stealthily if you look at an angle). If that's not what you want, Versatek "Opaque White" ink gives decent results. For printing other colors on black, doing a coat of white first (with the same screen) will make the colors much more visible. That's how I did this shirt, for example.
• For low-resolution designs (see "science", etc.), a low threads-per-inch monofilament screen material works well (61 TPI fabric from Dick Blick).
• The 125 TPI fabric works better for moderate-resolution screens, halftone patterns, etc.

Doing your own printing is fun if you enjoy hands-on things, doesn't cost much, and lets you do a lot of per-print customization if you want, with different colors, streaks, multiple prints... but can also take a lot of time. It's really only worth it if you enjoy the process. If you just want to get a t-shirt made with minimal effort, there are iron-on sheets that go in a desktop printer, or there are many companies with web sites that you can pay to print your custom images on a t-shirt.

Have fun.