How do I avoid classic beginners misstakes?

I'll chime in to say that flasy, pretty courses don't necessarily create learning. Yes, we should adhere to visual design principles, but if you're just starting out, keep your designs clean and simple. Try not to be intimidated by all the flashy gamification out here. Above all else, use learning theory and brain science to guide creation of your eLearning.

You are asking a very difficult question IMO.  There is never a 'classic' person, your background and existing skills will be different from everyone else. I don't want to disappoint you, reason why I pop in. Will you use Adobe Captivate for those courses?  Personally I have been a professor/coach/trainer since decades on many levels and for many topics. As musician I have been teaching (classical) flute playing to children and adults. As professor and engineer I have been teaching in a university college, both technical topics but also management and ICT. Having developed workflows for small construction companies with ICT for cost price calculation and project management I have coached and trained a lot of adults in those companies, but also immigrants from many countries looking for jobs in that industry. That looks similar to your 'history', correct? Interactivity is VERY important, and it took me a while when I started creating eLearning 2 decades ago to make the switch. Same is valid for teaching online, the difficulty of such a switch is too underestimated. 

Just couple of tips:

• Do not opt for a very easy tool, you'll bump too quickly on limitations.
• Take the time to learn to know the tool, no need for certificates.
• Give the learner as much control as possible, and use lot of interactions.
• Have respect for your learners, don't force them to do something.
• Audio is often neglected but is very important. Bad audio can cripple an eLearning course, which is not the case with poor images. 
• Keep your goals in sight (you have those skills), but you don't need to tell your learner what they are, they will be able to deduct them from your course.
• Offer them self-assessments, and don't limit to the eternal MCQ or T/F questions, there are better ways. My students loved them, although they didn't like exams.