How can you perform arbitrage (benefiting from pricing inefficiencies)?

Could you provide concrete examples? Also, let's say a stock trades on the NYSE and TSX (BNS for example), and the prices are apart by about .5%, could you perform arbitrage in this case, or am I getting the wrong idea? I mean how do you buy a stock or commodity and sell it on a whole different market where the stock/futures contract is not registered? Thanks a lot