The other day we learnt how to jack up a vehicle properly by using axel stands and a trolley jack, first we jacked up the car at the front on the cross member with the trolley jack, then we put the axel stands on the sides of the car to keep it stable then after making sure the car was stable then we jacked up the back of the car on the cross member
http://www.youtube.com/watch?v=L7YQjPAIr0Y

http://www.youtube.com/watch?v=q8KEytEW68Q