Lots of signs. Keep a list of homes for sale in the area in different price ranges, and always have area comps for the home you are sitting, buyers love to see them.

Barry Kessler gave you most of my tips. Be sure to get people to leave their contact info too. When I did open houses sometimes I'd have a drawing for a dinner out or a cash card or other prize. Great way to get a real email address and phone number from visitors.

For me:

Planning.

Signs.  And lots of them.

Exposure - online/offline.  

Information - have it available 

The Right Attitude - don't sit at the open house - treat it like a cocktail party. Greet - Meet

We have a 7 point plan.

Great planning and preparation

Johnny Davis pre-marketing everywhere! Start promoting it at least a week in advance and keep some door prizes, raffles etc.

Free ice cream scoop coupons in summer and many other ideas one can think of.

Lots of online promotion. Let the neighbors know in plenty of time to tell their friends and coworkers. Give them an invite to come early for a preview an hour before the general open. It makes them feel special. Have a drawing for door prizes and put out lots of signs, I like to use a flutter flag.

I agree with Ron- hold a private open house for the neighbors. In my opinion it's a great way to get a good solid return on your efforts.

Maybe have a lender at your open house to pre-qual buyers. You will determine who's ready now- then you can focus your efforts there.

Have the open house in the late afternoon- maybe 3pm-6pm.

Most importantly- advertise the open house. I feel like there is not a lot of effort that goes into marketing an open house. Its done just to pacify the Seller.

Agents put up their signs & maybe some ballons & hope for a miracle.

Our Mls has reverse prospecting. I send each agent  an invite to stop by with their client. If they cannot come by. I tell them to send their client with their info. They sign in with their first name and their agents info. I then send text to agent to follow up. 

Don't let anyone view the home until the first open house...that gets you lots of open house activity!

Advise your Seller to not have them.

They just don't work in my area. I've tried many things and so have other agents. They are just a waste of time in my market.