There are certain principles which help us to improve our skills and habits of learning. They are simple, yet, we tend to ignore them.
Allot time and list your tasks: Plan and list your study/work in advance and prioritise them according to importance and urgency. Be realistic in allotting time and the plan. If this is not done, you will end up wasting time with unsatisfactory results. With planning, you may even save time for leisure.
Have a clear purpose: Keep the benefits in mind as a motivating factor. It helps you to decide what and how to learn and to focus with an aim. This is more relevant when you are desperate or feel hopeless.
Create a congenial environment: Choose a place conducive to study, and which has a pleasant atmosphere with good facilities. The desk and other furniture should be convenient and comfortable to work/study. Arrange the material for easy access at any point of time. 
Method of study: Choose your best study time, either morning or evening, which is called your ‘prime time’. Take breaks. It is better to have modest goals. Keep the study modules to manageable size, by breaking into smaller pieces. It is easier to estimate the time taken for each such piece than the whole. In addition to short breaks, introduce variety so that the mind gets refreshed after the break or change. Decide in advance whether you want to browse, read selectively and ignore certain parts. This principle should be applied in taking notes while reading. Taking notes improves your concentration, makes you feel productive, serves as a memory aid and saves re-reading
Keep to the schedule and follow the plan: The tendency to leave one subject (study/work), for a more attractive one should be avoided. Completing incomplete work will take more time. Complete the projects in the order planned. File the material for easy access for future reference/ retrieval. Otherwise, even the best notes you have made become useless.
Key study skills: You learn better when you can relate what you have read or learned earlier. Then the mind is prepared to assimilate the new knowledge and fit it into a category that makes meaning to you. Therefore start with what you already know. Browse through the study material keeping in mind what you want to learn. The mind will subconsciously look for new knowledge. Browsing calls your attention to what the mind thinks is important. Then you will be able to relate the new information to the ones already existing in your mind/brain.
After browsing, concentrate on getting an overview, by reading through the index, synopsis and views from reviewers, if any. Look for main points which are usually the headings, or the first or last sentence of paragraphs. For basic knowledge, in many cases, an overview may be sufficient. If you wish to study the material in detail, you have to do a closer reading. Even for this, it is not necessary to read the book/material word to word. The overview tells you which part or aspects of the book are important and need a deeper study. Don’t get bogged down by a difficult concept or passage. As you read further, it may get explained. Later your subconscious mind will work on it and help you to understand it. An early review of what you have absorbed is a key step in organising new knowledge and remembering it in the long term. Psychologists suggest a 35-minute study is an ideal time to review what is learnt.
Notes are useful for recording information. Organise material in a manner you can understand when you refer to them later. There are many ways to do this depending on individual tastes, choice and purpose - like taking quick notes and then condensing them while reviewing/ rewriting; using pictures charts, diagrams or matrices to aid understanding/ remembering the subject. While taking notes during a lecture, concentrate on the key words or points of importance depending on  your needs or interest. Notes could be in many forms - underlining key words, highlighting the main points, comments on the margins on the material itself. The notes should be easy to handle/ carry/refer/ retrieve. 
You may like to further distill the notes to key words which will help you  recall the details using your memory. Use different creative techniques. If the study requires significant amount of learning, the method of ‘little and often’, called the ‘booster method’ can help to boost your mental capacity with short periods of revision. 
In short,
*Pay attention and concentrate to absorb the essentials.
*Relate new knowledge to what you already know.
*Repeat, review and practice.
*Learn by doing where necessary.