People like to be lead. Making decisions is somewhat mentally difficult/draining and people like to be told what to do (I've noticed this in areas like social settings and designing landing pages).
*led
That was my thought, too: This is a fairly simple but apparently effective bit of dating advice.
Don't invite someone out "sometime". Propose having dinner this Friday at 8 pm. Or better, dinner this Friday at 8 pm at Chez Whatever.
If they don't like Chez Whatever, you can negotiate on this point. Or maybe 8:30 pm is better.
Anything other than a clean reason for declination, including the proverbial "Perhaps another time", is "no". Well... You might still follow up to be sure. Again, with a specific proposal.
I also like the idea of a sort of "non-date". I'm going to be doing some (cool to me, at least -- I'll be having fun) stuff. Want to join in?
If you're enjoying yourself, you're probably going to be a lot more attractive, anyway.
This is also a great way to get dates: you don't "ask" them on a date, you merely invite them to go on a date that you'd already planned. It works much the same way as you prescribe. You're actually implying: "I'm going to go do something cool with or without you, and this is my invitation for you to join me _if you wish_."
Additionally, you can't be stood up if you never solidify your plans to revolve solely around one other person.