what are some things i can do for retail/office space open houses to make them successfull?

Are you making sure that you dress them out? Make it look like they are already leasing it. At least one or more offices. Even a few plants around in the place. Talk with some office furniture rental places. Offer for the potential tenants, for their contact information, the name of a moving company, office leasing company, design company, i.e., a network of help, that once they sign a contract with you, you and your network will take care of the rest, even at a possible discount, if they contract with you with-in a given amount of time.

Make sure they look occupied and ready to go.
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Curb appeal - inside and out. If attractive enough, they will WANT to have their office or store in your building. Ample parking, well lit at night, cleaning team provided, any other perks that will make your property stand out from the others on the market!