[Manuela]

With children (8 - 12), even with true beginners I like teaching them how to introduce themselves : "I'm Mary"
" I'm Bill" then have them shake hands with me in turn and say "Nice to meet you" "Nice to meet you too". THe whole class helps out the children who are shy.
Then I teach them to clap hands, shake their shoulders, snap their fingers, shake their heads, shout OK, slap their knees, stretch their arms etc when they respond correctly to these orders I sing " If you're happy and you know it" and they just do the actions.
If there are books to hand out I also teach them
"Here you are" Thank you" "Not at all"
So by the end of the first hour they can introduce themselves, offer things,say thank you and respond politely to that and can understand a number of orders that get them familiarised with parts of their bodies.

I liked the two activities listed above in this thread, a lot. Have tried out the
the Snowball thing, didn't know it was called like this. It' s an activity that comes in handy for revising vocabulary learnt so far too.

[Bilingualdiva]

Cool... I've never heard of the Jeapordy warmer... will use it soon..
Here are some I use with my high school kids.. works for adults advance class as well.
I ask the students to think of an adjective that describes them using the first or last Initial of their first or last name.. (in case there are any Y's or Z's in there) then studetns volunteer to go around the room and name the person and their adjective
or
I ask students as they walk into the class to cut a piece of string... any length they choose.... once everyone has their piece of string I ask them to say as many things about themselves for every wrap around their little finger ( thumb if it is a big class)
or
I have an assortment of magazine pictures of houses and homes cut out.. as the students come into class I ask them to select a home they would like to live in... on the back of the picture is a number ( the numbers double the house made of straw is #2 and the mansion is #2) when all have pictures I ask them to turn the picture around and find their mate, they must then tell their mate why they chose the house they did and their info ...name age.. etc..... give five or ten minutes (depends on size of class) once they have done this using the number order 1-??? have the pairs introduce each other to the rest of the class....and tell why their partner pick the house they chose...

these are very successful.. it gives the class a feeling of trust and gets them speaking the language or if they are beginners they find ways of comminucating using body language or what ever little bit of the language they might know..
beware... I teach classes of 35 ...when they are this big it takes at least two days to complete the warm up..35 kids 42 minutes....if your teaching time is longer kudos.....