In this case, the neighbor was expecting a dozen people. I have a tendency to "do" dinner parties for 6 (including us, two other couples/four singles, any combination thereof) every month or six weeks. Then twice ayear a party where anywhere from 20-50 people show up. In the days of my youth (haha), the latter parties were every other month. My neighbor was insane with fear because she'd rather planned that she'd have 8-10, then got RSVPs for 14. In fact, she had tons of food and drink, and everyone had a wonderful time. But she never relaxed, which to me is the key to a good party. If you cannot relax, your guests can't. I've lived here for a little over 3 years, and she keeps asking me my secrets. I'm trying to narrow it down for her, but sometimes it just comes down to liking people, food and drink. BUT ...
I agree, doing as much in advance as possible. For a large party (over a dozen), I make sure there is very little that needs to be done last minute.
Once I've lived somewhere long enough, I always ask a freind or freinds to come early, or at least right when I put the 'start time' on the invite. One thing that is awkward is having someone you don't know well be the first guest to arrive, and you're still running around getting last minute stuff done. Make sure your first guest will be a friend who can pour a drink, etc, if you need to spend a minute making sure there's no spinach in your teeth.
Go with local favorites. This is where I was amazed that my neighbor, not an experienced party-giver, took her trial by fire with a sushi party. It was a bold move I'd never have made!!! It turned out good, mostly because she and I also sat down and made sure that there were many dishes for people who wouldn't eat sushi --- yakitori (sans liver) and nege maki. So, it goes to show that maybe I'm wrong!!!!
Crowd people. I can't stress this enough. I had a huge home in Florida at one time, and people who knew each other gathered in various parts of the house and didn't mingle at all. Before and since (and at this party) people introduce themselves and each other, and rub shoulders with people they might not if there was more space. I once had a friend who was in Korea for a business trip (in military parlance, a TDY), and met someone who had just been stationed in Hawaii. On a freak chance, one asked the other if they knew Claire and Jerry. "OH, yes!!! They throw the best parties!!!! How do they know to invite such strange people???" I was so complimented when I heard this story (I was in Virginia at the time).
Which leads to ... don't think that your guests have to have a lot in common. They already have office parties, club parties, etc. Most people will honestly like meeting different people.
Which leads to ... introductions. This is very important, and something people are getting worse and worse at. If I'm introducing someone who has had family here for seven generations to someone who just moved here, I try to find something, and usually there is. "XXX works at the stone quarry, and you like to garden. XXX is a great source for paving stones, you need to talk to her!" Even if you have to reach, it works. But do your best to bring people together, and find a common place.
But the biggest thing, to me, is to be relaxed and enjoying the party yourself.