Great suggestions and I was pretty bad at it myself and I had inattentive ADD so that didn't help. No one had ever heard of it at that time so they didn't know how to help. Nowadays I work with HS kids every day and I see all levels of organization--and disorganization! The one thing that I always tell kids is that if you never did anything else except learn the vocab, it would probably be enough to pass any class except algebra. My favorite website for flashcards is
Simple free learning tools for students and teachers | Quizlet
The next thing I tell them is that when you approach a new chapter in a textbook, look at all the bolded and italicized words. They do that for a reason--to make them stand out, so they must be important. Many kids are afraid to ask the teacher for help, or they will only ask during class and never after or before school. Most teachers are delighted to help and will develop a favorable opinion towards them if they ask for help.
Of course one should never, never ignore the study guide for a test, but you'd be amazed at how many of them do this. Or they fill out the ones they know and skip the ones they don't. Often the text follows the SG pretty closely.
For notes, it helps to find what works. I heard once of a lady who doodled all of her notes but she could tell you what the teacher was talking about when she saw the star on the corner of the page. Mindmapping makes some really attractive looking notes and may be fun for a lot of kids and they're even pushing the method for adults these days.
Mind Maps - Mind Mapping Training from MindTools.com
Coach your son on test taking skills b/c this will help him for the rest of his life. I have a pi$$-poor attitude towards standardized testing but still push those skills for all they're worth b/c who wants to spend a lot of time studying only to do something stupid on the test? Like not doing the easy ones first and then not having time to finish. Not reading all the answer choices and choosing an answer that seems close but there may be one better. Not eliminating wrong answers to cut thru the confusion of having too many choices. Ignoring words like "always" or "none." I could go on but you can look these up and practice with him.
For English: you'd be amazed at how many kids sit down to write a paper and put down one sentence and yell for help. Of course they have not done the research and they have not even thought about making an outline though the teacher has stressed it highly. I help them figure out a basic format and number the paragraphs--usually 5. I tell them the first paragraph tells us what they're going to talk about. The 2nd--4th paragraphs talk about it and the last paragraph tells us what you just said. Then we usually fill in at least 3 details each for P.2-4 and save the topic sentence for last. Some kids are mentally incapable of doing this though--saving the first for last I mean.
Sometimes they have to read hard books though this has dumbed down so much I can barely believe it. A senior class is reading
Night? Great book but 9th grade or lower level. (We read Jane Eyre in 8th grade and that will show my age!) What I have found though is that when kids tackle a book that is rather archaic and wordy and they just want to stop after the first paragraph, if they stick with it, the language will start to resonate and it will become more understandable. When I read Shakespeare in college I didn't think I'd get thru it but the rhythm of the language soon caught me up and started to make sense pretty quickly. If they just can't do this, then I really don't believe that it hurts to have them watch the movie, look up a simplified version like No Fear Shakespeare, or listen to an audio recording. You can find a lot of this stuff free on the net or in your library. This website has lots of free audio books:
3000 Free Audio Books + eBooks, Download for iPhone, Android, Kindle and more! Cliffnotes is great too but they should probably check with the teacher, as some of them consider it cheating. I don't though.
Youtube often has stuff too and I found a great film version of Othello on there.