Spying on the competition may not be the most highbrow thing to do, but it’s extremely effective. Think of it this way: There are several companies that do what you do. If you want to know what works, you could review your records and see which products or pieces of content have done best. Or you could multiply all that by how many competitors you have, and use their work to find out what gets the best results.

This gets even more attractive when you realize how easy it is to spy — i.e., gather information. Here are eleven tools to make your content espionage successful. Most of them will also give you insights into how to improve your own site, and information about what your audience is interested in.

Google Alerts has been around for years. It works as well as ever and it’s a snap to use. Go to Alerts, enter your competitor’s name, or a keyword, or the name of a competing product. Choose how often you want to receive an update and which email address you want the update sent to. And that’s it. Google will send you alerts when new content appears on the Internet that matches your query.

Majestic is a well-known SEO tool, but it can also help content marketers. Use it to see how many backlinks your competitors have, plus where those backlinks are coming from, how they were accrued over time, and what anchor text leads visitors to the site. If your competitors are guest posters, this is an essential tool to find out where they’re getting published.

3. Topsy

Want to know which tweets, photos, videos or links have gotten the most activity recently? Topsy to the rescue. This social media monitoring tool will also tell you who’s most influential for a given keyword. That’s handy information if you want to invite someone to co-host a webinar, write a blog post, or review a product. You can also see which topics are trending.

Any affiliates reading this are in for a treat. SpyonWeb.com lets you know all the niches your competitors are in, and all the websites they own. Just type in their URL, Google AdSense or Analytics code, or IP address and Spy on Web will dish on all their other sites. Because it will also tell you which sites are hosted on the same IP address, this tool is worth a visit if you do any shared hosting.

Spyfu is well known among pay-per-click users, but it is helpful for anyone with competitors online. Spyfu will show you which keywords your competitors are advertising on, their rank, and roughly how much they spend per day. It also reveals keyword information, keyword-ranking difficulty, and which keywords are driving the most traffic to your competitors’ sites. There are free tutorials if you want to become a power user.

Do you like distilling things down to one number? This is the tool for you. The marketing grader reviews websites and social media activity, compares it to a series of marketing checklists, and delivers a grade accordingly. It’s a clever way to create a marketing to-do list fast, and a nice concise way to rank how your competitors are doing without getting into the details.

This is another tool that will give you a single number for each site, but it goes into significantly more depth than HubSpot’s tool. You can get a report on any site for free, but getting the action steps to improve it will require signing up for a 7-day free trial. If you’ve got the time, and want to do a more thorough comparison of your competitors and the opportunities for your site, this is a good place to start.

This is another tool that will give you a to-do list of how to improve your website and search engine rankings. It also lets you compare your site to three other competitors. While it’s similar to the prior two tools, I’m including it because it’s nice to confirm the information these sorts of tools give us.

This is another tool that’s been around for years, but it’s still as valuable as ever. Google Trends will be especially helpful to location-based businesses, because it’s one of the few tools that will show you which cities or regions are most interested in a given keyword. If you happen to do on-the-road training, or perhaps want to do a book tour, a visit to Google Trends is a must.

This tool can compare one Facebook page to another in terms of fans, growth, engagement, interaction, and service level. It’s a good way to gauge customer service responsiveness, and how well your competitors are staying on top of their social media work.

Want to find out how much social media attention a page has received, but can’t see any social media icons to give you counts? Head over to SharedCount and paste in that URL. You’ll see all the stats for that page in an instant.