This may not apply in your case, but a good place to start might be setting it up in google so you can track the metrics. See what is bringing you the hits, and amplify that.
I suggest you get the free Google keyword tool, look at the theme of your website, then use it to research the 'seed keywords'
As you providing information about health, travel, entertainment and many more to your user's then its good to target keywords those are similar to these tabs.
you may use some keyword tools or google adwords. using keyword tools you can see all of the related keywords that you may use on your website, and the higher the monthly searches, the more chance your website will appear on searches