The general rule about the venues is that very often, you can get a space for free. Your targets are big coworking spaces, hackerspaces, makerspaces, universities, local companies, and startups. These are the places that may be willing to offer you space for free (especially during weekends).
The setup should allow you to sit everyone comfortably in small groups (teams of 3 + 1 coach). The best setup is just square tables (or two tables put together) with 4 chairs around them.
Remember that everyone will need power! Often the venue can offer you this, but if they can't, just ask attendees and coaches to bring one power cord each -- this way you will have more than enough.
Internet is crucial, so ask your venue provider if they have tested the WiFi before. Be prepared for some problems, so have all the material (tutorial, bootstrap, etc) downloaded and saved on a couple of pen drives. You can use this script to download everything you need.
It is possible that the venue will claim they can handle Internet traffic, but during the workshop, it turns out they can't. It's a good idea to ask if they have previously hosted programming workshops for 100+ people.
It's also a good idea to have some backup mobile internet and to create a hotspot for attendees if the internet is not working properly. Make sure to check - especially during the installation part - if there are problems with the Internet.
A good atmosphere and friendly experience are extremely important, so if your budget is big enough, don't think twice about printing some posters, buying fresh flowers or bringing nice tablecloths. These small little things can go a long way toward making a better experience for everyone. We all like nice things, right?
Check our Do It Yourself chapter for more ideas. :)
There are a few small, cheap practical items that are really useful to have:
Scissors, string, sticky tape / blu-tack for hanging posters, bunting etc.
Spare pens and paper for drawing diagrams or making notes.
Tissues to wipe up spills, or in case the bathrooms run out
Sanitary products for the bathroom are a thoughtful touch and might be appreciated!
Garbage bags - there will be a mess to tidy up!