bringing a gift is a standard and well appreciated gesture - to female hosts, guests could bring flowers while for males hosts a fine bottle of wine is always a good idea - food is not well received unless specifically requested on the invite. in fact, bringing food can be interpreted as an implication that the party will not have enough food or that what is being served is not up to certain standards.

as fars as bringing additional guests, one should be aware of whether the host is allowing extra people to the event - when in doubt, one should ask beforehand and detail who the additional guest would be.

during the cocktail party, guests should allow the host to socialize with all of the attendees, as the host needs to interact with everyone in attendance, trying to get too much time or attention is not appropriate, and just minimum attention should be expected.