It perrty simple, value is very important these days. What as an instructor are you bring to the room that is of value to the student? More information isn't always valuble to the modern student, they need to feel involved in thier own learning. Empowering the student with the tall task of discovering a new subject. The way that best works for me is throught presentation and questioning technique that involves the student without ritacul. Have fun with teaching and the student will adapt to have fun also.
usually the older students are making new career moves so they're more open and ready for learning it has more value to them verses the younger student who is unsure of what his future holds and is he/she ready to work hard with long hours while his friends are having fun.
The motivation to learn comes from the want, either to know the information or the want to be able to use the information for personal or financial growth.