How to use the trademarks in our content

Any experts here on trademarks and related stuff? 

Last few weeks I have been reading a lot of information on trademark laws, violations etc. The more I read, the more confused I am!

Aren't we allowed to write Dell, Facebook, Windows etc in our content? For each word, should we say 'it is a  trademark of so and so company'? If that is the case, we can hardly find any word which is not a trademark and every single word we write should be accompanied by a trademark disclaimer!