There seem to be enough places on the inter-wily-web claiming to give good pointers about how to get free upgrades (dress smart casual, ask descretely at the gate etc). I've always been sceptical about the success rate of most - the only guarenteed option given is to use airmiles - so not a free upgrade then!
I split my trips between Economy/Business pretty equally - try not to smirk when self important travellers have the 'walk of shame' to the other side of the bulkhead after being told in no uncertain terms that they can't have that inviting seat near the front.