RE: Prepare to tow or be towed.
I've towed a number of boats that found themselves in distress.* They were almost always either out of fuel or had electrical problems.* I did most of those tows back when I had a 23' sailboat pushed with a 8 HP outboard.* I'd rig a bridle to the stern cleats and a line off the bridle to the other boat.
But I doubt I'll ever do it again in less than a life-or-death circumstance.* I read an article from BoatUS that said that almost always you are not going to be covered by your insurance company if anything goes awry with the tow.* Simple things like a line parting and swacking someone, a cleat pulling loose damaging either or both boats or persons, etc etc.* The article stated that if your boat is not set up and insured for towing you're on your own if ANYTHING goes wrong.
Or, maybe BoatUS was just trying to keep good Samaritans from taking some of their tow business.* But, I'm going to go with their recommendations.* Which were; call for help, stand ready to lend assistance and take personnel onboard if things get bad, but don't tow the other boat.