One of the problems that I come across trying to reach novices the correct position on a bike,is with regard to saddle position. They all want the saddle too low, they all want to be able to touch the ground while seated, and none of them will listen.
One particular novice that still wanted to ride , but was kept having muscle problems, would not raise his saddle, and eventually I took him to a Gymnasium. We set up the bikes as he wanted, and rode for 5 minutes. This rider was fit, local club runner, but could not not hack it on a bike. After 5 minutes he had the usual leg pains, so got the saddle height to the height he should have had it. No leg pains, and no lack of confidence as the bike could not fall over. This gym also has the Reebok spinning bikes, which have all the possible adjustments on them. Saddle height, for and aft saddle, stem lemgth, rake, bar height. You name it and they have it. We then got an instructor to set the bike up for him, and then readjust to lose the final aches. 2 hours later, and I couldn't get him off the bike. He was still minutely adjusting things. Not me or the instructor, He was.
He has now turned into a respectable biker, but it did cost him a new bike, as there was no way he could set up the old one to the new style that he wanted the bike to fit.