The three major considerations for a venue are room size, wifi and parking.

Teachmeets works best in a non-lecture or classroom layout. You will need a room with round tables if possible as it gets people talking to each other which is the primary aim. You will need a room that's not too tight for space as attendees can move about, especially for Soap Box time and allow people to get up and go for more tea/coffee or a drink without disrupting a whole row of attendees. The better the venue infrastructure, the less to worry about.
From experience, a venue with poor Wifi or poor broadband connection can be a huge obstacle to overcome. More on this below.
Good parking helps to get your Teachmeet off the ground and gets attendees in the right frame of mind. Consider an attendee rushing to attend a Teachmeet fighting rush hour traffic on an empty stomach spending 20 mins trying to find parking close to the venue is not going to arrive in good humour. Easy access and location well sign posted especially at night from where people have parked to the venue is really smart and professional and helps people to arrive in a more social frame of mind.

Room setup

It is very important to check the venue before you decide to use it. Ensure that the room you see is the one that you use as sometimes “a room like this” that is shown might be a mirror to the room that you will use. It might have doors, plugs etc. opposite to what you have planned for.

A room with plenty of space is a venue with great potential. Round tables have found to be very effective in getting people to start chatting especially if they are attending by themselves. Lecture formats have been used before but people tend to sit at the back and along the edges, leaving huge gap in the centre which can be off putting to some presenters.

A good venue will have loads of plugs available. It is important to have enough plugs around the podium or presenters area so if you have a few extension cords, this should be ok. In locations where there are few opportunities for people to recharge their devices, you should let me people know to arrive with devices fully charged.

Soapboxes which are 15 min long, which give an opportunity to showcase something with a bit more time for demonstration or discussing. The idea is the group should be small enough to huddle around a laptop in a corner of the venue. In an average venue, aim for 5 soapboxes, one in each corner and one in the middle, if you have 15-20 per soapbox huddle it seems to be optimal number. Sometimes you will find some soapboxes more popular than others so you might to flexible in managing that. A good venue will have some break out area which will allow soapboxes to spread themselves out a bit. You will find not everyone will go to a huddle or will drift between a few of them. Where you have a large audience (over 150 -200) it can become very difficult to manage in an inflexible venue so it may have a bearing on your decision to run soapboxes. Also don’t allow anyone to take over the podium to run their soapbox.

Some Teachmeets have been live streamed using ustream, Google hangout, Skype, or Flashmeeting. You do not have to do a streamed event it but if you do, you will need to plan for it in your room layout.

You may decide on having two screens and projectors in the venue. The best projector should be used for the presenter and should be viewable from all parts of the room. CESI Teachmeets would have the #tmcesi twitter stream displaying on a second screen as a backchannel.

It is a good idea to reserve the space in front of the presenters for TM related activities such as seating space for the host, spot prizes for the raffle, location for the live stream camera and for the person managing the twitter stream.