1) THE BASE: Ask yourself where you want to start. A building is strongest and most stable at the base. So that being said, you want to build a strong and stable foundation on the subject you want to learn. Concepts, rules, understanding play a big role when learning a subject. Grasping the fundamental ideology of a subject is the beginning of formulating the bases of understanding the core concepts. So in other words get a general picture of the subject and read the history behind it.
2) START SMALL BUT BROAD: Every subject has a broad category and a specific category. The more in-depth you go, the more confusing it can become if you don't have the general knowledge or a broad understanding of that subject. For example, you're not going to understand Calculus 2 without learning Calculus. Or understand how your brain creates memories or thoughts without understanding neurons. So by researching, reading, and analyzing the broad categories of the subject you can learn slowly by understanding the small sections within it. This will jump start your thinking process by having the idea of the whole picture while focusing on a small section of the subject.
3) PRACTICE: So in mathematics, one needs to continuously do problems in order to get better. In English, vocabulary is increased by reading often and taking time and learning new words. With practice comes connections. Your brain will naturally connect information to other information. This establishes a base for connecting ideas together which will help you learn the subject.
4) Notes: Know yourself! What works and what doesn't! Flashcards, writing notes in bullet points, sentences, paragraphs, or just memory! Test yourself by reading something and 5 minutes later write down what you remember! What ever you don't remember is the things you study harder.