Use your three seconds wisely.
That’s about as much time as you have to capture a reader’s attention, so don’t waste it with meaningless fluff, clichés or meandering prose. Make every word count.
The lead paragraph (or lede, as the old-school journalists would call it) of whatever you’re writing needs to convince readers immediately that it is worth their time to press on and continue reading. A boring beginning will result in a quick end.