Before you get too far into creating your course, do some research, if you haven't already, into how many courses already exist that cover your topic. It seems that so many instructors create a course and then wonder why, after a couple weeks or a month, they only have 1 or two students. Many times it's because 100+ other courses already exist that cover the topic.
Don't overprice your course. Most Udemy students are not accustomed to paying more than $10 for a course, and a good number of them never purchase a course unless Udemy is running a sale (I am that way too).
Others may disagree with this, but I would recommend not trying to make your course perfect. Your average earnings per sale will only be $1-$4 so it's just not worth going for perfection. I'm certainly not saying you should create junk. But you will be much better off creating multiple good courses instead of fewer, or one, perfect course. Udemy is strictly a volume business.
If your course is in English, make sure your accent, if any, is minimal, speak slowly and make sure your grammar is correct. If I purchase a course and I have a difficult time understanding the instructor I will get a refund.
I'm sure others will chime in with other suggestions.