I arrive on time, as that's just the polite thing to do and I'm not fashionable enough for fashionably late. I also like hanging out with people before things get crowded and/or loud, though I enjoy that too.
First day at my active duty station in the air force I show up 10 min early and some e5 staff sergeant tells me I'm late and proceeds to tell me if I'm not 15 min early I'm already 5 min late...fun times
As close to exactly the start time as possible. That's when I was asked to arrive, so that's what I'll do. While I'm with many folks here in wanting to arrive early to avoid being late, parties are the one exception. I think it is more rude to be early to a party than late unless it is at a public venue where I can hang out while waiting without imposing on the host.
I arrive slightly early (5 mins early) because I always make up an excuse to leave early.
My pet peeve is when there's a party agenda (6pm arrival, 7pm food) and if it's 730pm and food still hasnt been served, I can kindly remind the host that I have to leave by 8pm.
When I attended parties in my 20s, this was a extremely common issue. But as I get older and have a significantly more mature group of friends, Im starting to not have to use my "leave early" excuse as frequently.
If I know most everyone there, especially the host, I show up on time.
If I don't know most of the people going, I show up like 30 min late so the social lubricant can start flowing a bit before they get introduced to their new best friend.
15-20 minutes late. Gives enough time for a few other people to show up, and 8/10 times the hosts will still be frantically running around trying to finish preparing if you show up right on time.
I'm not fond of parties myself, but when I go to one, I get there on time, wait for the food, then leave with a full stomach. I may wait for leftovers to take home, but it depends. All I care about is the free food.