The header is the first indication of the content of your internet article. The average visitor will stop for no more than 2-3 seconds before deciding whether they want to read what you have written or should they simply move on to something better.
The article header should be clear enough to summarize the key point of the article while also be engaging/ inviting enough for the reader to want to know more.
Tips for Internet Article Headers (Source: The Yahoo! Style Guide, Chapter 4)
Quick Tips for Paragraphs and Sentences for the Internet
Keep them brief: Ideally no more than 25 words a sentence and no more than 2-3 sentences in a paragraph.
Frontload the information: State the most important point of each statement and paragraph upfront.
Use numbered lists when the sequence of events or numbering of the items is important. For example – Steps to follow in the recipe or Top 5 Beach Destinations