Well, the S 50 is basically the S 45 (same lense and hardware) but upgraded with a 5 megapixel CCD instead of the 4 megapixel one. Because it's got a small lense you're not going to get the -best- clarity out of it (probably won't look quite like a professional small model shot) but it should be good enough. You can focus up to 10 cm with it, in macro focus mode, and 30cm with the normal mode. It's capable of full manual focus, timing, and aperture settings, so that's a plus.
For best close-up shots you'll want to put the camera on a tripod and/or an immobile surface and use the momentary timer to take shots, or use the remote (if it came with one). The internal flash is best suited for shots taken at over 5 feet (typically), so unless you're taking shots at 3 feet I'd strongly recommend against using it - though you can get some pretty decent stills at that range, still, with (non-digital) zoom (don't use digital zoom - it'll just pixelate the image and make it ugly).
The aperture and timing settings will depend on your lighting. I recommend getting two (or three) shop lights and placing them about 5-10 feet away from the object (depending on the strength of the lights and the shadows you want to have in the photo) you're going to shoot, at 45 degree angles from the computer (or so - adjust for the lighting you want, again). The idea is to try and prevent shadows from being cast.
Then either use the automatic focus features of the camera on the object and/or fiddle around with the aperture and timing settings to get the desired result. You'll probably want a smaller aperture and longer timing for a still object (I
think).
I should note, I'm not a professional - I just dabble. But this is what I've observed and what I've done - I've got half a dozen decent photos, at least, with my Powershot G5.
Here are some shots I've taken...
http://hodgens.net/gallery/main.php?g2_itemId=2272