Tip #3: Tell her what she NEEDS to Know
If you have a simple surprise, like washing her car and filling the gas tank, go for it with no advance warning needed! But some treats are more complex and will be more enjoyable for your wife with at least some preparation on her part.
For example, would she prefer to be dressed a particular way for the dinner with friends? If you organize a surprise birthday party and she shows up in sweats and an old t-shirt, you might see a cringe of embarrassment instead of a smile when the crowd jumps out and yells “Surprise!”
If there is a situation in which you know she’ll enjoy them better with a particular head’s up, give it to her so she isn’t caught totally off-guard.
Aren’t sure whether that’s the case? Here’s what you do: ask her best friend(s). “Would Sara want to know about the surprise birthday dinner so she can look nice?” And the friend might say “Great idea, but don’t tell her it’s a dinner. Tell her that you need to stop by a restaurant to meet your boss and drop something off, and you want her to come in and say hello. That way she’ll want to look nice anyway.”
When in doubt, use her friends as your best allies!