I've been getting better at doing this, and I've read several books about it. All of them are kind of overpriced for what they actually tell you. Some of them contradict each other. Some emphasize using peripherial vision, while some emphasize using a finger to guide where you're looking.
There's always a precariousness between where you're skimming more than reading and where you're able to comprehend everything. It's up to you when to press ahead through what you think may be fluff and go into high gear.
The best book about it that I have read is Breakthrough Rapid Reading, mostly because it presents several possibilities that you can try to find the best technique for what you're trying to do. It also has good drills that will help you, although the best way to summarize it is "take something, read it, then drill to read it twice as fast... repeat...".
The most basic step is not to verbalize what you're reading at all. Most people out there can double their speed if they were doing this by fixing that. The next step is to reduce and then eliminate the amount of time you spend backtracking; if your remove that you again can double your reading time somewhat quickly if it was a problem for you. After that, you can experiment with changing how you focus your eyes and limiting the time you spend refocusing on letters.
When you're aiming for full comprehension and somewhat less speed than other faster techniques, one way that really works well is to kind of break the text into 3 line blocks. For each block, park your eyes on the middle line and alternately hop between two focus points three times soaking up the words above, then in the middle, then below. Then jump 3 more lines down, etc. This method gets rid of a lot of up/down movement and saves you good amount of time for almost no comprehension penalty.
