I was interested to see what people think here because although not an Instructor with a capital "I", I have sometimes introduced people to my club, and sometimes to caving itself; and acted before the club created its web-site as an ex-officio contact via the county library service.
As well as the technical matters - where I prefer "use the methods and equipment you judge best and safest for the situation" to over-prescription - I wondered if anyone would mention the beginner's committment. Burt does, from experience in instructing kayaking. Christine hints at it I think.
I found many enquirers lacked even the committment to take up my invitation to ring me to arrange a trip, even though I'd taken time to and effort to answer carefully all their questions in their original letter (pre-wwww). I could never think why. Had I done something wrong? I believe now that such people may be the harder to deal with if they do turn up, because I think that they expect full, "instant" gratification, preferably from others' efforts. I've seen similar elsewhere so it's not confined to caving.
Christine's pre-trip questionnnaires may help to minimise having to struggle with obese or excessively unfit beginners by putting the onus on them to decide if such a pursuit is right for them; or if they think improving their fitness first would be adviseable. It may also encourage the more committed while discouraging the dilettantes who want all the onus to be on the leader.
Even more importantly it may weed out the minority who ignore advice or instruction even when obviously needing it. I've not personally encountered this but I know of one woman who has recently been refused membership of at least two major clubs through risking endangering herself and her team-mates by her attitude.
Obviously most of those who try caving once or twice decide it's not their thing and take up Synchronised Crochet or something instead, but I find it rather sad and a bit offensive when people proudly tell me, "Oh, I've been caving" then it becomes clear that they think Caving is summed up by their few basic trips. If they said they'd tried but didn't like it then, fine: at least that's honest.
Many people now do want and expect others to think for them, be responsible for them; yet want and expect instant, full results or answers with no skill or effort on their part, in many walks of life. Do you caving instructors find many of your clients are like this?
On slowing down the "tigers", I'd suggest flattering them by asking them to "help" - before handing them the rope bag or whatever!
BTW whatever happened to the waist-length, that de-rigeur caving accessory of the '70s? A sewn tape sling, it was always handy for giving someone a bit of security and a hand up a tricky little climb or smooth slope.