It is now over a year since I have sadly had to depart from my university upon obtaining my master's degree in mathematics. I have since obtained a job as a programming contractor, however classical mathematics done with pen and paper is still the love of my life. Luckily enough, I still live within two hours of my old campus, and I was able to obtain an external library card, which is my ticket to look into all the topics I missed out on for want of time (not all mathematical).
If anyone among you has a similar experience, I would like you to share your techniques, too. Be advised that my way might not be very efficient nor lend itself to people who still need to study for exams or have deadlines, because I am no longer under these pressures.
Scouting. The closer a field is to my interests, the more books I already know to be suitable or unsuitable for me to learn from. For me, the most important criterion for a maths or theoretical physics book is to have numerous exercises on many different levels of difficulty and abstraction. I also prefer the books that use familiar notations to my lectures, and those that are written in my native language. Least importantly, a little pet peeve of mine is that I don't like it when books are set in Times New Roman because I find the font hideous and I honestly can't bear to look at it for long periods of time.
Frequency. Due to my day job, I am usually unable to clear more than an hour each day to sit down and study. I tend to use this hour to either read through a chapter and fill in the blanks between the formulae and draw pictures, or to attempt to do the exercises when I am done with the required reading for them. If an exercise seems boring and not what I wanted to learn from the book, I still tend to look up the solution rather than not considering it at all.
Intensity. Because I am no longer under the pressure of cramming and deadlines, I might take longer or sometimes lack the motivation to learn a topic, but I also have the liberty to take a minute and ask questions about it for which there was no time during my student years. Unless there is an elephant in the room requiring more urgent attention, I always tend to go through three things to look for: Examples and applications, characteristics of the generic case and the singular cases, and analogies in the language of other fields.
Surroundings. I tend to learn at my desk for when I need to write or take notes, and from my bed when I don't, although I reckon that the latter is a bad habit. Although during my earlier time at uni I used to learn with classical or Latin music or even commentary, I now tend to find it too distracting and prefer silence for learning. For obvious reasons I learn alone now, but I have always found it more fun and also easier to have a study buddy.