Before you start posting, I highly suggest building a buffer of pages. If you have a weekly or monthly update schedule, it can be very stressful trying to finish each new page before the next update, and it doesn't give you any flexibility if you get sick or anything.
So my biggest piece of advice is to build up a buffer! I finished my entire 40-page first chapter before I started posting anything online, so I had plenty of time to make new pages. Being weeks or months ahead on updates means for a stress-free production schedule!
Aside from that... Just do it! The only way to get better at drawing comics is to draw comics! So if you're at all worried that you don't know what you're doing, don't worry about that at all! Just make sure your lettering is legible and you'll be fine. Good luck!!