Influencers can recommend you — or they can hurt you. They can bring your name to a completely new audience and provide unique insights because of their relationships.

Developing strong relationships with them is important — but how do you know who they are? And more particularly, how might you assess the power of their influence?

Here are 10 tests that can help:

1. The Google test: When you search for an influencer's area of expertise on Google, does she appear in the first few entries? Or further down the list? If you search for her name, is she referenced within a number of different sites, or just her own? Beyond Google, check the Bing search engine, as well as her website's Alexa rank.

2. The social follower test: While quantity isn't everything, it is an important factor. How many followers/friends/connections does the influencer have on Twitter, YouTube, Facebook and LinkedIn? And if there is a particular social network within your industry, how many followers does he have there?

3. The activity level test: How active is she? How often does she post original thinking? How many shares, comments, likes and retweets?

4. The social influence test: There are a number of websites that purport to assess an individual's (or a brand's) influence. What is his? Check out Kred, Klout and Naymz.

5. The economic test: How much does she charge for mentions, advertising or sponsorship? The ability to charge for access is one indicator of the economic value of her influence: the more she charges, presumably the higher her influence. Be wary, however: many influencers see this practice as compromising their independence and objectivity, and don't "sell" their name to anyone.

6. The traditional media test: Perhaps we have come full circle, but too often influence is being defined narrowly as online influence. The traditional media test speaks to his recognition outside of the blogosphere and twitterverse. How often is he quoted or does he write in newspapers and magazines? How often does he provide his perspective on radio or television? Is he regularly called by national media, or only by more obscure (or local) outlets?

7. The longevity test: How many decades has she been doing what she's been doing? Expertise, profile, connections and influence don't "magically" come into being all by themselves it builds over time.

8. The fancy title test: Some people are given influence by virtue of their jobs. One definition of influence is an individual's seniority multiplied by the size of his organization. This is not a problem, but if one of your goals is to build relationships with this type of influencer (a noble goal for a host of other reasons as well), remember that once he leaves his job, you will need to start over with his replacement.

9. The author/speaker test: How often does she speak on her expertise? Is she paid to speak? How many books has she written? Are the books traditionally published, or are they self-published and of dubious quality?

10. The community involvement test: Influence also stems from what people do beyond their day jobs. This may mean leadership in a professional association, faith community, neighborhood ratepayers group, school PTA, kids' sports league or his own baseball team. The more active the person is, the greater his influence.

Ultimately, the most important test is always relevance. The question of influence is not complete unless you address the question of who he/she is influential with. If a person or organization has influence with an irrelevant target audience, then why should you care? To you, that influencer is irrelevant.

This week's action plan: Who are the influencers in your market? This week, spend a few minutes identifying them, and then put together a plan to build stronger relationships with them. And if you are looking for more, consider how you might become a more powerful influencer yourself. Look at the tests above: Do your current marketing initiatives move you up the scale on each?