A speaker is considered an instant expert and has high visibility. Consultants are experts and need visibility so that potential clients can find them!
ANYONE can speak; we all have experiences and knowledge to share. Even if you only have one year of experience, no doubt you have done something, and you may have a case study you can talk about.
Make sure your bio or intro describes you well. For example, stating you are an “independent pentester” or a “computer security consultant” is much better than a “geek who likes to hack computers.” It should be obvious that you are hireable!
A great speech contains stories – and stories from your previous work or consulting help emphasize that you get things done, what kind of things you do, and add color and credibility.
Although you obviously want to speak in front of people that can buy your services and those who have influence over those that can buy your services, you don’t know which speaking venues will work for you until you try.
For example I have two friends who speak regularly at the RSA Conference, and one gets lots of consulting work from those talks and one gets very little. You don’t know what will work for you so try speaking, at least initially, anywhere that will let you speak.
You get better at speaking by speaking! If you are hesitant, perhaps even afraid to speak, consider joining an organization like Toastmasters. They are a “nonprofit educational organization that operates clubs worldwide for the purpose of helping members improve their communication, public speaking, and leadership skills” (ref: Wikipedia).
Get out there and speak! No, you do not have too, but it is NOT hard and I’ve gotten lots of business from speaking.