A few years back, I wrote a popular post on SEOmoz featuring a set of questions I felt were a litmus test for SEOs seeking to charge for their consulting services. It's time to revisit that, as many of the answers have changed and the baseline has moved (forward).

If you're in the SEO business professionally - either as an in-house marketer helping your team with SEO or as an SEO consultant (solo or agency), this knowledge should be second-nature. And if you're hiring a new SEO or seeking interview questions for someone to bring onto the team, feel free to use these to separate the wheat from the chaff:

1. Which is more likely to have a positive impact on a page's search engine rankings and why - 10 links from 1 website or 1 link each from 10 different websites?
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2. Explain the difference between the following items and how the search engines treat them - 301 response code, 302 response code, canonical URL tag and meta refresh.
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3. How can the meta robots tag impact how search engines crawl, index and display content on a web page?
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4. Who are the top 2 search engines (as ranked by share of queries) in the following countries - the United States, United Kingdom, Russia and China?
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5. Name at least 3 elements critical to ranking well in Google Local/Maps/Places search.
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6. What aspects of social media marketing have a positive impact on search engine rankings (apart from the value of direct links from the social sites)?
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7. List 5 tags/locations on a page where employing a target keyword can have a positive effect on search engine rankings.
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8. Describe the distribution of search query demand and what is meant by the "fat head" and "long tail."
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9. Name 6 tools/sources that will display a list of external URLs that link to a webpage.
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10. What are some ways to positively influence the ratio of pages a search engine will crawl and index on a website?
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11. BONUS! Describe the concept of topic modeling and how modern search engines might use it to improve the quality of their results.

I'll post answers to the questions in the next 12-24 hours and link to it from this post. In the meantime, I'm looking forward to the comments and discussion of answers, including any additional suggestions you have for "litmus test" quality questions.

UPDATE: Answers to the questions above are now live here. Enjoy!