My first couple of talks were in front of huge groups of people at well known tech conferences and they all were blatant disasters. I wish I would have made so many things differently...

BUT: I DID START GIVING TALKS!

That in itself was one of the biggest achievements in my professional life! So if there is one advice, for me it would be: Get going!

Put all thoughts of: "I need a better topic." or "I need a more suitable occasion" or "I need a smaller audience". Just go. Stop worrying, hand in your CFPs and start moving. Build momentum and get your feet wet.