The aim of organizing an event is to get people to attend. But then you need a way to get them to know that the event is coming up. You need to promote the event.
If we don't give them, how do they get it?
Consider the CTA as what potential event attendees have to do to indicate interest in the event.
The CTA could be an event registration form. It could be registering for the event on an event website. It could simply be an RSVP. Or in the case of paid events, it would be getting event tickets.
Develop your call-to-action as you start planning the event.
Your CTA will persist across your chosen promotion methods. In other words, RSVP, or "Register", or "Buy Ticket", or what you choose, should be seen anywhere there are details about this upcoming event.
Make the registration process as smooth as possible. This will create a good user experience for those who have an interest in your event while they are registering.
Even if this is a physical event, you can still have ways of engaging people from offline advertisements. You can have people manually registered at some locations or by some chosen persons. You can put phone numbers on banners. Just find a way to dictate potential attendees. Besides, it will help you budget better.
One hidden advantage of your CTA is that it permits you to harvest emails and phone numbers of potential attendees. You can send bulk emails and or SMS to them, for reminders, as the event draws near.
Where affordable (or if it's a great event), you can have an event website. The website could have a countdown to the event, event agenda, promotions content, speakers, about your community, ...
What would they gain if they attend this event?
Answers to that question should be the content of your promotions. Remind prospective attendees about the benefits of being at your event.
Make them feel what they have to lose if they don't take part in the event. You are marketing, so you have to be good at copywriting. If you are not, community members can help. Create good copies and use them everywhere there are details about the event. People will be sold and wouldn't want to miss.
Write in an active voice. Use the pronoun "you". Avoid much text or use bullet points (where possible).
You should have more content for promotions. Stuff like event agenda, about your community, benefits of technologies involved, ... can also be part of promotion content, and not just benefits of being in the event.
However, the benefits should be more than other details.
Graphics (and Videos)
Design flyers or get help for this from core team members.
Good designs tell the viewers the most important things first (have a hierarchy). Good designs breathe (have space). Good designs are attractive and keep the viewer getting all the details (have good branding and color combos).
Flyers should have the event's call-to-action, date and time, venue, content, speakers, title, and logos (where applicable). All those may not fit, or might not even apply to you (you might not have speakers for example).
You can also split what you put in the graphics across other graphics. So that you would have more than one flyer. You will notice that you might end up having a particular event flyer for the whole promotion. That's fine.
It is not mandatory to put (all) the "event benefits" on graphics. Remember that good designs have enough space.
Videos stick more than pictures. Videos show multiple images and add sound, whereas a graphic is just an image at a time. Where achievable, consider having some animation or video for promotional purposes.
Where affordable too, consider using billboards and posters. You might follow this path if your community is large and you have great expectations of attendees. This applies to physical events and is a common choice for paid events too.
If you have people coming to share some knowledge at the event, please have flyers for them. Like have flyers that follow your event's flyer template, but this time, with the speaker(s)' images and about them (and what they will talk about).
When you confirm a given speaker, request their details: bio, name, and photo. Use the details for the speaker flyers. Give the speakers their flyers ahead of time and ask them to share.
Most of the time, your speakers are popular and have earned an audience for themselves. Getting them to your event is already promoting your community. The extra step of themselves mentioning that they will speak at the given event is an addition to the event's promotions.
Your community members should be part of the promotions process. Ask them to share flyers and links regularly. Ask them to talk about the event. Make them feel that preparations are steady are going on well so that in turn they will anticipate great things and attend the event.
Have the core-team work on promotions. Delegate tasks. Consider having a promotions committee. This committee will be in charge of everything hype. It could be some core team members. It could be them and some community members too. Preferably choose social people.
The committee might handle everything promotions from beginning to end. Just devise a way to follow up and be sure work is being done. Set goals, targets, and timelines.
Leverage other social gatherings in your locality. For example, make announcements for the event in religious gatherings, sports/club activities, other tech communities (and their events), ...
The core team and community members should follow suit. If they are in any place where they could share about the event, please get them to do so.
It's fine to collaborate with other communities for tech events. The collaboration helps with promotions too. It is mutual leverage worth mentioning. Both parties tell the people about each other, so yes.
Your community should have social media platforms you use already. Post regularly on these platforms about the upcoming event. Use engaging captions when posting the images.
Have a hashtag (if you deem it fit). It could be a peculiar hashtag for the event or a hashtag your community always uses.
Tag and post the speakers.
There might already be core team members handling the community's social media. They should continue and just up the game. The promotions committee can also help. A content calendar is in place. Use tools with scheduled posts if you know how it works.
Where affordable, reach out to influencers and get them to share and talk about your event. You can use online or local influencers depending on where you host your event.
Where affordable, use paid digital marketing. That is pay social media platforms to advertise your event too. You will also get potential attendees from there.
Promotion is are marketing and is not an easy task. If you plan well, you will get it right.
It is okay if you exhaustively promote your event and the attendee count on the event day is low. On average, the conversion rate of advertisements is about 4%. So if you have a greater than 4% of your RSVPs attended your event then you should be proud of yourself.
With regards to your event and the entire marketing, remember the following:
Do not over promise and do not under deliver.