As a host, past speaker, often invited speaker etc... let me just throw in a few points.
I think selling yourself to the event host is possibly the easiest part.
THEN providing education, entertainment (and depending on the seminar's business model), a worthwhile sales offer that converts, THOSE are the points that really matter.
I'd personally recommend you focus in on that.
Can you present in an engaging and entertaining way? Or do you just step on stage as the genius, but one who can't teach it to their audience? Does your audience go "wow that guy is smart, the stuff he talked about sounds interesting, but I have no idea what I'm supposed to do with that information"? Can you make them laugh? Weave in a story? Entertain them? Create interactivity?
If you can do the above, most hosts would want you back and give you sharp testimonials.
If you're just another "expert" who steps on stage, rambles, throws out big keywords and really leaves no value for the audience then that feedback will work against you real fast.
Tying into that... you either have the "get paid to speak" or "sell from stage" models (generally speaking). I doubt you'd land too many worthwhile "get paid to speak" gigs and I'm not sure if that's really the most profitable way to go either way. Feel free to look into the ins and outs of that model.
However, for the "sell from stage", the host also needs to know that you have a compelling offer, a high value product/offer that you can EFFECTIVELY sell to the audience. So, assuming the host did a good job and planted wide awake, enthusiastic, target prospects in a room for you... you SHOULD be able to build an irresistable offer AND sell it.
So, again, before focusing on things like PR and testimonials and references and marketing yourself to events as a speaker, I'd really recommend you nail down the above 2 points.
If you have THAT on lock down, the rest really becomes easy.
General points though for marketing yourself...
- video clips of you speaking are useful but MAKE SURE they are high quality. Don't post cheesy cell phone camera footage. But 2-3 minute excerpts from a couple of previous talks... it especially helps if we can hear the audience react, laugh, ask questions, applaud or whatever. But a host would want to see that you can be on stage with posture and confidence.
- testimonials from other events (anywhere you've previously spoke at). This is a big one.
- testimonials from audience members (those who have seen you speak)
- bullet point pow-pow-pow of your accomplishments... basically, without exaggeration, but just by pointing the spotlight on the RIGHT parts of your past... make me get a sense that you are a God in your area of expertise.
Other points...
Create a speaker@______.com or speakerinvites@_____.com email address and forward it to your assistant or create a Gmail account that it forwards to and create a "fake assistant" name.
As a host, lie to me, make me feel like you're so well accomplished that you MUST have an assistant. If your emails are coming from randomguy@hotmail.com and it's just me and you talking, that's fine, the JV might still move forward.. but it plants the image that you're still not as accomplished as you could be.
So dress it up. It's about marketing. Women wear high heels and push up bras to, uhhmm, highlight their features. But it's really a lie (they're not that tall or "well endowed"). Same thing here. Lie to me. Make me, as the host, feel like you're quite busy and accomplished.
Then marketing...
You SHOULD do a few practice runs. Contact your Chamber of Commerces or local Meetup.com organizers or other Associations... do a couple of free (or low paid, or whatever) practice talks. In your case, it sounds like you've already got that.
I have one speaker this year (at my CanadaMarketingSummit.ca coming up in September, [end shameless plug]) who is a GENIUS in his own rights and I KNOW he can teach and I KNOW he can sell. However, he has a new topic that I'm more than excited to have him talk about. But since this particular presentation is new, I suggested that he create the powerpoint presentation and run a few webinars (to his list, with some JVs). I told him this will bring in some cash for him either way but mostly, it gives him practice before he stands in front of my 200+ audience.
Once you have the practice talks done... then build a database of all the associations, chambers, meetups, tradeshows, seminars, workshops, bootcamps (keyword search each of these) in your area. Find organizers, event planners and other circles of influence. Ask for referrals. Send small thank you gifts for those referrals.
Oh, and get professional photos done.
One of my past clients has a team of 3 guys that runs 3-day workshops each month. Great content at the workshop but they had a cheesy 1990s website and terrible photos. Professional headshots and $100 revamp of their site added a massive leap in their credibilty and professinalism.
anyways, I'm jabbering now. Hope some of that helps.