Walk over with no pretense...if that person is speaking with someone else be polite and wait until there is a lag in the conversation and introduce yourself to that person and to the others. "Hi, I am __________." If that person isn't speaking with anyone, just say "I think this is an interesting place to be" or a topic that would be appropriate for why you and that other person may be in the room. Just an opening, nothing serious. Then the conversation can move on from there.

Personally, I don't have a problem talking to anyone, and I don't mind when someone I don't know walks over and introduces him/herself. Make a connection and go from there! Good Luck!

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A blessed thing it is for any man or woman to have a friend, one human soul whom we can trust utterly, who knows the best and worst of us, and who loves us in spite of all our faults.