The grander your scheme, the more help you’ll need from others. But the more people involved, the more likely things are to go awry. So make sure you have backup plans for as many reasonable scenarios as you can think of—even if you two are the only folks concerned. For example, what’ll need to change if your girlfriend’s running late? What if she doesn’t feel like going where you suggested? What if she or you get sick? As anxious as you may be to get engaged, postponing your proposal can sometimes be your best option.