Telling a 19 month old off

[Chillaxed]

Hi all.

Would appreciate everyone's thoughts on when to start telling a wee one off, and how. Our 19 month old son understands simple phrases now - sit down, give x to me, etc - and is prone to throwing a wobbly when we take his dummy or a favourite toy, so we'd like to ramp up the verbal discipline a touch. At the moment we generally ignore him or say 'no' in a firm tone, but all that's done is make 'no' his favourite word.

Thoughts and experiences gratefully received.