What should you do when an unexpected opportunity--a new client, a new direction, or a new partnership--comes knocking? Should you leap at the chance? Vet the prospect thoroughly, looking under rocks for hidden dangers? Or stick resolutely to your existing customers and original business plan?

It's a question I often ponder because that's the nature of my business. Projects and business offers frequently arrive in unexpected ways from unexpected directions. Though I think of myself as primarily a writer, I'm currently overseeing a website. In the past, I've answered phones overnight at a crisis center, sung to audiences in yoga studios, and helped create Wikipedia entries. Once, after being begged by an acquaintance who loved my cooking, I spent a Saturday afternoon making a large batch of carrot halvah and earned myself $200. I've also turned down many offers--editorships, article assignments, book projects, and full-time jobs--because they were the wrong opportunity, or the right opportunity at the wrong time.

How do you decide when to jump on something and when to let it pass? Start by asking yourself these questions:

1. How does this opportunity benefit you?

Usually the answer is pretty straightforward and comes with a dollar sign in front of it. That's a must: Being properly compensated for your work, product, or service is a minimum requirement for a good opportunity. Beyond that basic benefit, what else is good about this opportunity? Is it coming at a slow time in your cycle, when you need new business to stay afloat? Will it give you a toehold in a new market? Does it come with premium pay? Will it get you in the door at a big, powerful company? Will it support a mission you consider important? Perhaps most important, will it be fun? You should be able to answer yes to at least a few of these questions.

2. What are the down sides?

Every opportunity comes with some negatives, so what are the negatives here? Will you have to meet tight production deadlines? Customize your product more than usual? Learn new techniques? Will you have to work with difficult personalities? Will you have to accommodate customers who aren't sure what they want? Those last two items are dealbreakers for me.

3. What's the best possible outcome from this opportunity?

You should never take on an order or project because of pie-in-the-sky hopes that doing so will rocket you into the stratosphere. But--keeping in mind that this is just a look at what's possible, not what's promised--are there wonderful things that could result from this opportunity? Is it the thin end of the wedge that could get you in the door at a big customer? Could it result in many more orders? Raise your visibility? Give you a powerful ally? Dream big for a moment about where this opportunity could go if everything goes really well. If that end result isn't something you want, then maybe this opportunity makes no sense for you after all.

4. What's the worst possible outcome you could have from this opportunity?

Everything comes with risk, but some things are riskier than others. If this opportunity requires you to lay out a lot of cash upfront, or offer lengthy credit terms, or hire extra personnel that you otherwise don't need, then consider what might happen if things don't go as planned. That goes double if this opportunity requires you for any reason to stop serving an existing customer. Go ahead: Imagine the worst possible scenario.

5. Can you take on this opportunity and still fulfill existing obligations?

If taking this opportunity will strain your resources so that you can't live up to existing commitments, you're better off passing it by. That's true even if the new opportunity is vastly more lucrative or otherwise better than the existing one. I don't know of any industry so large that people don't talk to each other, and a reputation for either delivering as promised or dropping the ball will follow you wherever you go.

6. What will this opportunity prevent you from doing?

Almost any opportunity comes with opportunity costs, so what are the costs here? Will it take you away from other work you want to do? Time spent with your family? Exploring new markets or new business directions? Make sure to weigh in these missed activities on the negative side of the balance.

7. How does this opportunity fit into your long-term goals?

This is probably the most important question of all. You have a mission, a vision, and several goals, both for the coming year and for the long term. How does this opportunity fit in with that mission, vision, and those goals? Will it help support at least one of these, or is it a detour? If this opportunity doesn't move you toward fulfilling your vision or meeting your goals, it may be better to pass it by. And if you don't have a vision and long-term goals, please stop reading this article immediately and go do some strategic planning!

8. Should you be pursuing something else?

Opportunities that land in your lap are wonderful. You don't have to pitch anyone and you know you have a deal already done. On the other hand, the customers who come knocking at your door are usually not the biggest or best-paying, or most high-profile. Is saying yes to this opportunity the path of least resistance because pitching a bigger, better customer would take more effort and involve more risk? If so, consider whether you're better off turning it down. And then go out and find a better opportunity somewhere else.