Using a continuum with opposing values at each end, ask students to decide where they would put various items/theories/ideas etc on the continuum. For example, useful _____________________ not useful, ask students to come up to the board and mark on the continuum where they would put a chocolate fireguard and why? You can discuss differences in opinion to start a debate. Useful for evaluation issues. You can also put several ideas onto the continuum in a ‘rank order’ eg from most useful to the least useful.