For those who can do speed reading, how did you obtain that skill?

Moderately long preface before my answer---for a good reason.

I can read very quickly.  (My sister-in-law once saw me open a card from her sister, my wife, close it immediately and laugh.  She said that I could not possibly have read what the card said and what my wife had written and respond. My wife simply said, "oh, yes, he did." and I simply quoted what the card said and summarized my wife's personal comment.)  My point---When I say I can read very quickly, trust me.

Reading and eating have this similarity---occasionally you eat over a relaxing 2 hour period and occasionally you "slam" down a quick protein shake because you are in a hurry.  My point---the actual speed you read something at will depend on the material and personal factors and goals at the time you choose to read.

Reading much faster than you currently do is a worthwhile and usually attainable ability. 

http://lifehacker.com/the-truth-about-speed-reading-1542508398

I can only speed read when reading non-fiction. When reading a history book for instance, read only the beginning and ending two sentences of each paragraph on each page. If a chapter seems to be less important, then read the first and last paragraph of each chapter. You don't need to read an entire book to get its point.

1. Stop talking to yourself while you read.
2. Cover words you've already read.
3. Understand eye movements. While reading, your eyes move jerkily, stopping on some words and skipping others. You can only read while your eyes are stopped. If you learn to make fewer movements per line, you'll read a lot faster.
4. Train your eyes to make fewer movements.
5. Set a pace faster than you understand. Many programs claim to increase your reading speed by training your reflexes first, then practicing until your brain can catch up. This has not been thoroughly studied. It certainly increases the speed you move through the text, but you may understand little or nothing.
6. Try RSVP software. If you can't reach your goals with the techniques above, try RSVP, or Reading Rapid Serial Visual Presentation. In this approach, the phone app or computer software flashes text a single word at a time.
   

Anime with English subtitles.