I think it will really depend on the goal for your group and what kind of people you want to attract. Generally speaking, they all comprise of one of (or both) these two parts: Showing work and working on art. Some have attempted to do actual workshops where people present techniques and teach the others, but in my experience this falls through unless there is a rather strong and dedicated organizer at the head. Especially since you're getting a lot of introverted artists together that hiss at public speaking
This is the format each one has, to give you some examples and get that creativity flowing:
Digital Artist Meetup: Most of the time is spent going around the room and showing your work from this month, talking about projects, and getting feedback if wanted. People can also ask questions about your process. This one probably has the most professional level people in attendance, so it fosters the most job, collaborative, and learning opportunities. We talk about things like taxes, pricing, and business, too. After the meetup proper, we go to a restaurant/bar nearby to chat more casually for a few hours (this is where the real networking happens imo).
Artist Jam: Purely time to work on your own thing with the chance to be social. They set up several tables and you can sit anywhere and do your craft. You get more out of it if you actually talk to people though, lol. It's pretty general and people of all skill levels/trades come to it.
Creator's Workshop: This used to be an actual workshop formula where we had guest speakers and demonstrations, but it ended up becoming more like an Artist Jam geared towards storytelling. So we get a good mix of artists and writers. Kinda wish there was still a dedicated person running it, having the guest speakers was cool.
Side Projects Club: This is a group to keep you accountable to your side projects on a monthly basis (like a gym buddy?). They have weekly meetups that are dedicated work time and once a month they have a meeting where you talk about your goals, if you met them or not, and what you're going to do for this month. Then they use the rest of the time to work on their thing.
Drink & Draw: This is a 21+ life drawing meetup. The organizer hires 3 nude models and has them pose for us throughout the night. We support the venue by buying alcohol! Despite its implications, it's not rowdy or anything. Very respectful and a nice atmosphere. Good place to meet more fine arts people or traditional artists.
If you were to start anything like these, you're going to need a reliable location and time slot, and you gotta reach out to the community at large through things like flyers, facebook, and meetup.com. And just like... keep up consistency and keep holding them, even if no one but you and a couple other people show up. It will grow, but it takes patience. ...Like a webcomic. Treat it like you would a webcomic.
As far as venue suggestions go, most the ones listed above are either held at local comic shops or the local technology library. c: