Go to the end of the chapter and read the chapter summary carefully. This is like the book summary on a novel, it tells you the boiled-down essence of the chapter. In the end, all you're going to remember are key points, so start here to prime yourself for what you are about to learn.
Start to read the chapter and take notes!
Make notes in your own words/notation. However you understand the material (as long as its correct) is more important than how the textbook explains it!
Textbooks are generally very dense and reading every word is time consuming and taxing. Skimming lets you get the big ideas without devoting so much to what is really not all that important. DONT READ EVERY WORD.
Keep a computer/phone handy to look up ideas/words if you need. I don't read anything - novels, textbooks, anything - without a device to look things up.
Write down key equations and define all the variables in whatever terms make most sense to you. It's okay to not fully understand it when you take the notes, you will understand them as you use them.
If you are at all a visual learner, look at the figures to understand the concepts. If it is a graph, give some time to looking at the axes and what they mean.
BOLD/ITALIC/LARGE-PRINT WORDS are stressed for a reason: they are probably specific jargon that you will need to know!
Embedded in the text (often set-aside in boxes or something), these problems almost always build very gently on the concepts just discussed. These guys are good way to test your understanding of the concept. If you get it, great, move on. If not, return to the concept and work through the example until you get it.
When you're done reading the chapter, re-do the example questions at the back of the book that you did to start. See if they now make more sense.
Look at your notes again and see if there are any improvements you can make: clearer ways to explain things, condense ideas further, better definitions, etc. Make those improvements. The chapter summary is a good indicator of what your notes should contain.