Mazel Tov on your new baby boy!
If everything is OK with your baby, his Bris will be on the same day, exactly one week from the day that he was born. That means if he was born Sunday morning, his Bris will be on the following Sunday. If he was born Sunday night after Shkiah, which is really Yom Sheini, his Bris will be the following Monday.
#1 Book a Mohel - To get started, you need to book a Mohel, as soon as you can. Many Mohelim are very busy, and while you can almost always get the Mohel of your choice, if you delay, he will not always be available at the time of your choice, and you will need to choose someone else. So don't wait around! The Mohel will want to know what day and time the baby was born, if it was a natural birth or a C-Section and if anything happened out of the ordinary. Choosing a Mohel is an important decision for the parents to make together. Before calling the Mohel, it would be a good idea to read my section, Choosing a Mohel. There is more to consider than you would expect!
#2 Book a Simcha Hall - Now that you have booked a Mohel, you should book a Simcha Hall. The Simcha Halls get booked up quickly, so again, don't wait around! Most Brissim in Eretz Yisrael are done in a Hall. If you prefer, you can do the Bris in a Shul, and have the Seudah in a Hall. The downside of this is that people have to go to two places instead of one. You can find a list of popular Simcha Halls in my section, Halls, Caterers and Gemachim. The list includes prices, addresses, and contact information.
#3 Book a Caterer - Now is also a good time to book a Caterer, but this is not as big of a rush. Usually caterers will accommodate latecomers. You can find a list of them in the Halls, Caterers and Gemachim section. The list includes prices. Please note that many caterers offer upgraded menus.
While it seems preferable in Halacha to serve Fleishigs by a Bris, the prevalent Minhag amongst Americans is to serve Milchigs.
#4 Shalom Zachor - Now that you have booked a Simcha Hall, you need to prepare for a Shalom Zachor! This will be the Friday Night in between the birth and the Bris. (If for whatever reason the Bris will have to be delayed, the Shalom Zachor will still be that first Friday Night) If the baby was born early on in the week, you can wait a little bit until you plan this out, but if the baby was born later, you are in a rush to organize everything as soon as possible.
You will need to buy beer, drinks, chips, seeds, nuts, chickpeas, candy, cakes, cookies, plastic, etc. Many people serve cholent as well. Some people may bring cakes and cookies etc., but try to stay on top of it. You don't want to run out of food. Obviously, not all of the above mentioned items are mandatory.
There is a Gemach available to organize your Shalom Zachor, for a small fee. You can find them in the Halls, Caterers and Gemachim section.
In addition, you will need to make signs notifying everyone where and when the Shalom Zachor will be taking place. If you already know where and when the Bris will be, you can include that in the sign. Make sure to word it as an announcement rather than an invitation. The reason for this is because when you invite someone to a Bris, the Halacha is that they are supposed to go. You should write the time for the Bris 15 minutes before you actually want to start, as people usually come late to Brissim. You can personalize the announcement, but here is a general idea: