I work in a school for adults, I use differente games as icebreakers. You can find lots of games on this site. You can also play board games that your students already know, for instance: the bingo (to practise numbers), cards (the UNO game helps you to practise colours, numbers), and there are many books with games that can be photocopied. Students speak without the pressure of making mistakes copying with the coursebook ;)

My students struggle when they speak even though they are intermediate. It �s partly because they are shy and partly because they don �t know how to connect all the words they know  correctly in a short time. SO to relieve their stress I suggest expressions or patterns they can use. For example  instead of giving them a  simple situation (If you �re in a sinking boat, what  three Items would you take? � with a very sort reading) and push to converse, I give a handout with information such as (1) Items: a,b,c,... (2)weather or season (3) patterns and expressions: I �ll take____,because the weather  is _____) Because they are adults, more choices make them happier (the number of items or others) while less patterns and expressions are always welcomed. 

Adult students don �t want to sound dumb so a correct or clear sentence structures at hand are like a seat belt.

Good Luck

I agree with ttuffl - it �s good to give people a model to work from. Maybe teach a few structures (even a grammar point) and then ask questions to practise that point. With my adult class, I recently did a session on "making suggestions". We discussed 3 groups of structures - those with base verb (You could ...), those with the infinitive (It �s a good idea to ...) and those with a noun or gerund (Have you tried ...?). The pupils had a printed handout with the structures on it and then we moved into an oral activity giving advice to others.

Role plays are another great way to get pupils to talk. They feel less self-conscious as they are not expressing their own ideas but rather those of the �character � they are playing.

If some pupils are more confident than others, you could try getting them to answer the first few questions, thus producing a model for the less confident pupils.