I've done it... Towed an old lugged steel five dollar bike home about 8 or 9 miles. I just strapped the front wheel to a fold out grocery rack on the bike I rode in on as well as possible with four bungees. The handling was really wierd, because the odd angle that the towed bike's headset was at would cause the towed bike to lean at odd angles in turns, which caused a little rear steer input. It's nothing impossible, just don't stand on the pedals while the bike(s) is(are) in motion.

Try this first: Stand in front of your bike, grab the bars, and lift the front wheel off of the ground. Walk around with it, but keep the bars level and the front wheel airborne. All of that wierd twisting force is what you'd be working against while towing a bike.