The number one effective way to increase reading speed, in my opinion, is phrase-slashing.
1. Take a magazine you can mark in, find an article you would have read anyway, and
2. Put a slash mark at every phrase: I pledge allegiance / to the flag / of the United States / of America, / and to the replublic / for which it stands / …
At first, you will find yourself asking yourself if it’s a phrase or not, but you’ll quickly settle this. A phrase won’t be longer than the width of your eye span (3-6 words). Phrases are the smallest true units of thought.
What you discover is how impportant prepositions and commas (and of course, periods) are to signal to your brain which chunks to gobble up. By physically making the slashes for about 5-10 sessions, your mind starts looking for phrases rather than words. This makes your brain start to look for thought-units (phrases) instead of words, allowing the author to communicate to you in thoughts rather than words.
Soon your eyes will make one “stop” at the high center of each phrase instead of each word, and you will stop “subvocalizing” every single word.
Try phrase-slashing for 5 times and see if you notice. If it works, do it until you read in phrases.