[enyafriend]

私 [watashi], 僕 [boku], 俺 [ore]

One should always address oneself as 私 [watashi] at all times. It is applicable to both male and female. It is a polite word for me or I.

For male, 僕 [boku] can also be used. It is a casual way of addressing oneself.
But 俺 [ore] should be used with reservations. It is a very masculine way of saying "I" and only used when speaking to similar age-group and very close friends within their circle. It is most inappropriate to be used in a forum where most are strangers to one another. The only time when you want use 俺 [ore] to stranger is when you want to pick a fight or trying to be rude.

For female, 私 [watashi] is the best choice in any situations. Though, thesedays, young and trendy girls sometimes do use 僕 [boku] to sound masculine. あたし [atashi] is also sometimes used to sound cute and affectionate. Then again, it is also used when one intends to sound rude or in a confrontation situation.

Though, you may want to use any one word for the fun of it, but I believe that if you want to learn, you should learn it the right way. Or at least, understand the word first so that you know what you are using and not just using it blindly. Have fun.

Anyone who has any Basic Japanese knowledge to add or to correct, or simply to give their two cents worth are most welcome to post or to re-post from other forums.