Dillon,
I'm an agent here in Tampa and have sold many a home at an open house. Here are the key factors:
1. Competition - You want to get AS MANY buyers and looky loos in the property at the same time. You want buyers to feel like everyone is in competition for the property. They'll feel like any one of these people might buy the house and they need to make an offer fast to not miss out.
2. Timing - You ideally want to launch your property as follows: On market Tuesday, Broker's Open/Caravan on Wednesday, Public Open House on Saturday. When your house hits the market on Tuesday, agents will generally call you that afternoon to ask questions. Tell them you're holding a brokers open on caravan on Wednesday, and tell them to come have some lunch. Bring any agents from your office that are available as well to fill in the broker's open. Let agent's show the house from Tuesday to Saturday, and then Saturday hit with the big Public Open. I recommend keeping the open house short, I personally like 11 am - 1 pm (although 10 am to 12 pm works fine too) I don't love later in the afternoon open houses because buyers have usually been out looking at houses all day and are a bit fatigued. Some may give up and not show. Remember the #1 thing is competition, you want them all there at the same time. Also be aware of sport schedules. On Saturdays in Tampa college football can be very big so get the schedules for teams that are big locally (Florida, Florida State, and USF to a lessor extent) and nationally (Alabama, Georgia, LSU, Notre Dame, etc.) and make sure your open house doesn't conflict with any marquee matchups or local games. I don't like Sundays for open houses. Too many people go to Church, and in the fall there's NFL to contend with.
3. Sign In Sheet/Follow Up - It's important to have all open house visitors sign in both for security purposes, and for marketing. I like to have a branded video tour of all my listings. I tell every visitor to my open house that I need to collect their email, because I know they're looking at a lot of houses and they all blend into one. But I'm going to send you a video tour of the property, feel free to share it with family and friends. I also promise them that this is the ONLY email they will ever receive from me. (We all hate spam, and let's face it most Realtors/Loan Officer's mailing lists don't really have anything interesting to say)
4. Refreshments - Keep it simple, but do put out some beverages and light food. If it's a morning open house coffee and pastrys/bagels is always great, maybe some fresh fruit. Always have some bottled water. (I know agents that put their contact info on water bottles but let's be honest, these are getting thrown out.)
5. Neighbors - Others have said it but I always door knock the entire block and invite them. Usually try to do this the day before but can be done the morning of. Try to get as many people there at the same time. Use the refreshments as a bribe "Come down have a cup of coffee and check out the house."
6. Engage - Try to engage everyone who comes through, but try to not make it be about the house. Ask them what they're up to this morning, if they have kids with them talk about that, if they're new to the area find out where they're from/what brought them here. People love to talk about themselves, give them the opportunity to tell you what they want/need without directly asking. You'll often find buyers here. Also, while talking to the neighbors that came to take a look, you may find sellers as well. I had an open house a few years ago where a neighbor came by and I got three deals out of it. She let me list her house, her boyfriend's condo, and sell them the new house they bought together. And now her sister is going to buy a house with me too. Don't discount anyone you meet, open houses are a huge opportunity to expand your business.
Bottom line, open houses are great. Before the pandemic, my entire business model was based on flipping houses with investors, and then meeting the surrounding neighbors at the open house. The pandemic REALLY put a hurt on my real estate business because of the inability to hold true open houses for a while. (I switched majority of my business to multifamily value add after that but still take the time to do listings and open houses today when they come to me). Put the time into it and you'll do well.