I have a pet peeve when being asked out (or, well, had–not much “asking out” goes on in long-term relationships, though it still goes for friend meet-ups): “Let’s do something.” It’s ambiguous. It usually leads to the equally annoying “What do you want to do/see/eat? I don’t know, what do you want to do/see/eat?” conversations.
If you’re doing the asking or suggesting, have a plan. Give it some thought before you just toss it out there! I get that you want to be open and accommodating, or maybe you don’t know exactly what the other person would like. In those cases, come up with some options: 2 different restaurants/movies/etc. (no more than 3 though–too many options is not a good thing) and give them a choice.
But have a plan. Always have a plan.
(Thus ends my soapbox on interpersonal relationships. Oh, who am I kidding, this whole comic is a soapbox on interpersonal relationships!)