A few broad suggestions may help you to select your rate(s) within the particular article:
Decrease speed when you find the following:
An unfamiliar word not made clear by the sentence. Try to understand it from the way it's used; then read on and return to it later.
Long and uninvolved sentence and paragraph structure. Slow down enough to enable you to untangle them and get an accurate idea of what the passage says.
Unfamiliar or abstract ideas. Look for applications or examples which will give them meaning. Demand that an idea "make sense." Never give up until you understand, because it will be that much easier the next time. Find someone to help you if necessary.
Detailed, technical material. This includes complicated directions, abstract principles, materials on which you have scant background.
Material on which you want detailed retention. The key to memory is organization and recitation. Speed should not be a consideration here.
Increase speed when you find the following:
Simple material with few ideas new to you. Move rapidly over the familiar.
Unnecessary examples and illustrations. These are included to clarify ideas. If not needed, move over them rapidly.
Detailed explanation and elaboration which you do not need.
Broad, generalized ideas. These can be rapidly grasped, even with scan techniques
Skip that material which is not suitable for your purpose. While the author may have thought particular information was relevant, his/her reason for writing was not necessarily the same as your reason for reading. Remember to keep your reading attack flexible.
Shift gears from selection to selection. Use low gear when the going is steep; shift into high when you get to the smooth parts. Remember to adjust your rate within a given article according to the type of road you are traveling and to your purposes in traveling it. Most important, remember: You must practice these techniques until a flexible reading rate becomes second nature to you.