Some people are born party planners; others are not. For those that are not naturals there are a few easy things you can learn from from those instinctive event masters.
1. Plan now, worry less later. There are tons of guides on web to help you. I have put together my own birthday planning guide. You can have it for free. Just fill in the three pieces of info, scroll down and hit submit:
2. Budget: I've performed at literally thousands of parties over the past 20 years. I have performed at parties with budgets of over $10,000 and at parties with $300 budgets. And by no means was one better than the other. It was all about having a budget and using it. I have seen parties ruined by not having a budget and sticking with it. What usually happens is one parent overspends and the other parent is mad the entire event because their partner didn't stick to the budget. Guests can feel that kind of tension. Don't let it ruin your party. Have a clear budget, communicate it with any other event planners, especially if it's your spouse, life partner, or your child's other parent.
3. Write stuff down. Relying on one's memory is almost a sure way to forget something. In my guide (available above for free) you will find a checklist of things needed for a successful party.
Above all else remember to have fun. If you are not having fun others won't either. If you don't like planning, delegate and if you have no one to delegate to, make a very loose plan and don't be afraid to let things happen.