For me, I didn't use clicker or treats. Magic was barely harness trained when I began him on jumps. He knew the basics, but nothing else really. Harness training is the major key step before introducing jumps. Through jump-work with Magic, I taught him how to respond to aids (right, left, etc.) you may wish to incorporate that within the harness training, but it may work better if you incoporate it on the course.
I started with thick poles (even a chunk of wood will work) laying on the ground, and with some poles on a brick too. The tallest jumps were maybe 4 inches and I kept him going at that for the longest time. He did great over the low jumps and I remember when he first jumped the 9-incher how I was so surprised and proud of him! Lol. Now he's up in the teen/20 range.
Anyway, the most importnant thing is to take it slow.
You don't want to rush into placing a larger jump, and you always want to make sure when you add higher jumps, you have previous ones so they hold their confidence on those and are ready for the larger ones.
I may begin training Magic on some agility work using a clicker, because he has responded to it well when I taught him tricks.
If you have any more questions, feel free to ask. You can PM if you like.
I also have a thread about getting started in Rabbit Hopping. I can dig up the link for you. I will probably start the online training program once the weather gets nicer
Emily