How to make search on all fields (title and tags as well as body)?
One thing you can do to control which fields are included in your search index is to go to your specific content type's 'Manage Display' page.

So go to Structure --> Content types --> Your content type --> Manage display.

On that screen, you'll see a collapsed section called 'Custom Display Settings'.  Just click on it to expand it.  You should see that you can check to enable the 'Search index' display to be customized (Usually only the teaser or summary is included for customization by default).  Check the 'Search index' box and save:



That will provide you with a brand new "Search index" tab on this screen.  Click on it and start customizing which fields you want to be included for this content type's search index: