To break the 'ice' on any gig - read the 'night' first to guage an approximate point, or check with the client.
What I mean is, judge the amount of guests by how many you were told would arrive.
It's a half empty / half full guage to go by, but you may know by now from experience.
It's not easy to judge - every gig is different.
O.k., is there food on the night or not.
If yes - great. At time of booking, I explain to all clients that the gig will 'take off' more or less after the food - 20-30 mins say.
Inbetween, as already suggested, play background. No one will immediately dance straight away....ask the client if it's alright to focus on pleasing kids with their requests until ITS TIME TO PARTY!!
On Weddings, after background, the First Dance (if asked for) is great to break the Ice for starting the Disco.
If no food, and just guests, read the night!
But I think that you're looking for particular songs to start a night.
Because every gig is different, it would be unfair to say "Yes - this is the tune to play...", but I'm sure we could all tell you what's a general track.
The only way to explain how I work is that (i think?!?) I tend to think in 3's & 4's. If I play an intro song, and people start tapping their feet or get up straight away, then I need a middle or follow on song. If that's cool, then a third. But the attention span of a crowd is so different to every gig, that's when you start reading the crowd and building the night.
But 3' & 4's will not work on every gig. It's an individual 'split second' decision, and you tend to go with instinct.
Note
look at some of the other threads on gigs and tracks played.
There are some good posts on typical functions / wedding functions.