To get a good page title in DNN when you create a page:

• Click the 'add' button to add a new page. 
• Only fill in the page name and leave the page title empty.

This way DNN will create a page title which corresponds to the site structure.
So it might be something like: "Home > Products > Productname"
If you fill in the page title field, DNN will just use the text you have entered in this field.

If you choose your page name's well and include a lot of important keywords, it will provide a good structure for search engines like Google.