Jenn, your party will be great. I am tempted to say, "Don't worry," but that's a pointless thing to say to anyone.

I will tell you what the experienced hosts who post here say over and over and over again: the secret to a successful evening is a relaxed host who isn't stressing out over everything.

I know that's easier said than done, even for experienced hosts. But here are some tips that help a LOT:

1) This is obvious: don't bite off more than you can chew. If you are pretty new to entertaining (and even if you're not), now is not the time to be trying 5 new recipes, 4 of which require a lot of attention at the last minute, for 30 people, on homemade tablecloths. Keep it simple. I think most people prefer that anyway.

Let's take your backyard party. It sounds like fun! Plan simple appetizers you can make ahead -- honestly, for a party like that, I'd probably just have a big bowl of grapes and and some chips and dip, maybe pita and hummus. Have some soft drinks, beer and/or sangria, and one kind each of white and red wine -- let the store advise you if you don't have a preference. Hard liquor too if you like, but don't bother with a full bar for all kinds of cocktails -- it's too labor intensive for you when you have guests. BBQ foods -- you know how to do that. 2 or 3 of chicken, burgers, hot dogs. Buns, condiments. 2 or 3 salads you like and can make ahead. Everybody likes pickles. More chips. Dessert: anything you can make ahead. Maybe brownies and watermelon and sorbet?
You'll know when to clear away the BBQ stuff and bring out dessert: when people have stopped going back for more of the BBQ course. Just put it out and let people help themselves; ask who wants coffee.
Don't worry about "and then what?" They don't need you to orchestrate activities. They will either play more games or just chat, and they will probably keep picking at the desserts and chips. Think about when you are the guest. Isn't that what happens? Were you bored and never wanted to come back? Of course not. You had a nice time and appreciated the hospitality. Your guests will, too.

2) Plan ahead. Of course it makes it less likely you have to run to the store twice the day of the party. But really I think the biggest benefit to writing stuff down is that it keeps it from circling around and around in your head and seeming like more than it really is.

3) This is the most important: This is about your guests having a pleasant evening, NOT your performance as a host. No one is judging or grading you, your cooking, your bartending, or your home. This wrecks the nerves of hosts who do an excellent job, because when the slightest thing goes wrong, they lose it -- they were focusing on the perfect fulfillment of their vision for the party, not on everyone just having a nice visit.

4) A perfect party is NOT a flawless party. Something WILL go wrong, or at least not as planned. Maybe it will be something you do, like spilling or overcooking something, or it will rain, or someone will break something, or one of the guests will cancel at the last minute. So what? That doesn't mean it won't be just as good an evening, even if you are disappointed about some item. Just don't focus on it, and certainly don't let your guests see that you mind in the slightest.

We entertain a lot, and I am sure that not ONCE has everything been perfect. But it's usually wonderful. And I notice that now that I have my confidence and have learned to go with the flow and not get upset when things don't go the way I've planned, not only do I have a better time, my guests do, too.

I mean, you say you've often been a guest. I'm sure you can think of lots of things that went "wrong" at those events. But it didn't ruin the evening, did it? I bet if you think of the very best time you ever had at someone's house, probably you can think of something that went wrong -- and almost surely it wasn't the most perfect example of entertaining you ever saw.

It's hard to have fun when the hosts are uptight and exhausted. So keep your plans simple, have confidence that your friends are there to enjoy your and each other's company, not to see if you rate five stars, and laugh off anything that goes wrong. I promise you a successful party!

Thank you so much for the very helpful tips.

I am a very easy-going guest and not easily bored; I don't expect anything in particular, I just enjoy the event, the people, and whatever is served. I drink very little alcohol so I don't expect that either. However, a few people (family members) in our life are not so easy-going.... they want what they want, seem bored, and will ask for a food or drink if it is not offered. I think they are the ones who led to my new anxieties about entertaining, worrying that the food, drink, activities etc. won't be good enough.

How delightful! :-)

Okay, so you just expect that they are going to behave that way. If they ask for somethng, just give it to them if you have it, and just say "sorry" if you don't. The important thing to remember is that if and when they do behave like that, it is NOT a sign that you failed at entertaining, and it won't ruin the evening.

Thank you so much for your tips! I'm new to this and I understand that there are TONS of things for me to learn in a party science) However, there are some rules that I've learned by trial and error:
1)Invite right people. It's not about some people's being "right" or "wrong" for parties. It's about inviting certain people to certain parties.
2)Keep it simple. I mean relaxed. If you are trying to hard to make your party awesome, neither you not your guests are having fun.
3)Choose the right music. Background noises can mean the difference between success and failure. Here's the hit of my latest party: http://wowmp3.net/music/the-great-gatsby-a-little-party-never-killed-nobody-mp3.html :)
4)Plan B. You can't plan everything perfectly and you want to know what to do in case something goes wrong.