For whatever reason, I've always enjoyed giving presentations.

As a developer, I've grown from giving the rare presentation when asked to frequently doing 'brown bag' talks and other presentations on new technology, projects etc.

I'd like to expand as a presenter and start giving talks in public, outside of just my workplace, and I'm looking for tips on how to get there.

At a high level, I'd love to know a good path to take & useful tips to help me grow from just giving internal talks to my group (10-20 people) to eventually be a presenter at medium-large sized conferences.

Here are some specific questions, but I will take any advice you can offer:

1. How much experience do I need to speak at user groups etc? I've been in industry for around 5 years, which pales in comparison to most speakers that I normally see.
2. What is a good venue for my 1st public talk?
3. What surprises can I expect when transistioning from speaking to a small group of friends to presenting in public to strangers?

I live in southern California and my background is mostly .net / web, so if you have any specific user group / venues those are also greatly appreciated.