how can i get a cannonball mould :s and wheres a good place to set a cannon up at.

If you've done the dwarf cannon quest, you can buy a cannonball mould from the guy in one of the huts above the dwarven mines.

 

 

 

 

 

 

 

You should set up your cannon anywhere where it's multicombat and there are several monsters around you.

Pedrahm answered the first question.

 

 

 

 

 

 

 

Where to put it, the Ogres under Blood Rune tower are good, rock crabs are too, pretty much anything in a multi area. Don't use it in wildy, you can't.

The Dagannoths in the Light House are most people's favourite. The Ogre cages North West of Ardy are a fairly good spot too.