americans and english use the same words that have different meanings. for example american pants=trousers english=underware american cell phone, where as english refer to as mobile or mobile phone. what im trying to say is looking down this route, some resarch on the subject of slang etc may help you identify more quickly. also as an english native the american accent is higher to me way the english accent is more monotone, for example "have a nice day" in american sounds to me more chirpy in sound simmilar to a teenager i guess, where as the english "have a good day" sounds more flat in sound. thats my own opinons but i hope i helped in some small way. regards james

The fastest way is to ask. In no way is it offensive in my American opinion. =May be different for the English, I admit.

Ask if they like soccer. A British person will almost invariably and indignantly reply "you mean FOOTBALL" :)

They usually have difference in the pronunciation of D and T. For example, little: it's the same words for both and it's the same meaning but it changes its pronunciation. Little in American English the T become like a R in Chinese. And Little in English is the same same pronunciation for T. The same happens to D.