Make up their mind for them
Some people take their sweet time making up their minds. If you really need their mind made up fast, make it up for them.
Nicely, mind you.
One way of doing this is instead of saying:
‘what do you think we should do here’,
the next logical step would be to say:
‘What do you think about option A versus option B?’
Or, you could just get straight to the point, and say:
‘We’re going to do this, is that alright?’
Depending on the person, sometimes this is the best thing you can do to push the project forward. If they really dislike the option, they will speak up. Which only pushes the project forward.