Definitely if you have the option to take a friend with you, then do so. If not then hang out by the bar, its the best place to catch other strays. For small talk, talk about the atmosphere ( not the clouds and stuff but whats going on around at the party) mostly ask questions, girls really like to talk about themselves and mistake that for in-depth conversation. I don't like to approach large mixed gender groups because it has the makings of an awkward situation written all over it. If you know the person throwing the party ask others if and how they know them that's another easy way to strike up conversation