You should choose a space for your event according to the kind of event it is, and make sure that it's large enough to comfortably accommodate all of your guests. Find out what's in the space - does it come with furniture or equipment?
A classic training session works best with an absence of tables, a loose configuration of chairs, and a flipchart. Training sessions often last for more than 3 hours, so you might want to make sure that beverages are available at the venue (in the form of a water cooler, or perhaps a kettle).