I would actually phrase this another way, "Be honest with me: If I asked you to refer me to one of your investors, would you recommend me to him/her or is my startup not there yet?"
1) Be specific. Which investor do you want an intro to, and why? I know my investors well. Some of them love meeting early-stage startups. With others, you are wasting your time unless you've already raised significant capital. Other times I can't help at all (recently got asked for an intro by a B2C company--I know my investors from a B2B perspective since that's where my company is, and I'm not sure who would be a best fit for a B2C company.)
2) Be real. If you don't have any customers/pipeline, traction, or even a working demo, you're not ready for investment. For some reason there tends to be a pervasive belief that a "napkin idea" can get funded. Maybe 1% of the time, that's true. But even with a previous exit under my belt, I still had to have some form of traction before I got investors onboard. If you have nothing except an idea, please feel free to ask for advice, but don't ask for advice on looking for investors, because I'm going to tell you to focus on traction first.
- First-time founder has to show traction.
- With a handful of successful startups under the belt, one can make do with a good powerpoint, a prototype and some customer interviews.
- With a long streak of victories, a napkin is just fine.
Ergo if you're not Steve Jobs, you can't get away with a napkin.