There are many strategies you can learn to sell your courses, to me the best and first one is to make quality courses... and notice I used the "s" for plural... you can not hope to make a course and live on that.. the more quality courses you'll do the more weight you'll have in Udemy system... and this will bring to more sales...
The season of failure is the best time for sowing the seeds of success (Paramhansa Yogananda)
