It's important to study English every day. However, don't exaggerate! Study for thirty minutes every day instead of two hours once a week. Short, steady practice is much better for learning than long periods on an irregular basis. This habit of studying English every day will help keep English in your brain fresh.
Give yourself one grammar goal when reading a new article or watching a new video. For example, try to write down each example of a form you are studying such as the present perfect. Use highlighters (colored pens) with texts to highlight forms that you are studying.
Don't just use one way to study English. Use a variety of methods which will help all the parts of your brain (multiple intelligences) help you. For example, if you are learning new vocabulary, create a word map, describe a picture, make a list and study that, type out the words five times. All of these methods together help to reinforce your learning.
There is nothing like having a few friends to study English together. You can practice the exercises together, have conversations together (in English!), and, as you study English together, help each other with exercises you may not understand.
One of the most important things to do is to study English using topics that you like. This will help motivate you because you will also be learning about a topic you find interesting while you study English.
Activate your vocabulary by thinking or speaking briefly about the subject you are about to work on. For example, if you are going to study English on topics that focus on vacations, take a moment to think about your last vacation, what you did, what you enjoyed, etc. This exercise will help your brain warm-up to vocabulary that you are likely to encounter as you study English about this particular subject.
Activate your grammar by thinking about the general grammar area before you begin to study. For example, if you are going to study English grammar focusing on the past, stop to think about what you did last weekend, where you went, etc. to help activate what you already understand about using the past. As with activating vocabulary, you'll help your brain bring up what it knows about the past in an easy way before you begin to focus on studying English grammar in detail.
Before class begins, or before you sit down to study English sing a song in English to yourself. Make sure to use a song that you understand and know very well. This short and fun exercise will help your brain focus on the English language in a relaxing manner. It's important to be relaxed when you study English! Singing a song also helps activate the creative side of your brain which can help you come up with more examples as your practice conversation or do some creative writing.
If you going to study English at your desk, begin by typing a paragraph in English. You can type about your day, your hobbies, your friends, etc. Anything will do. Typing helps activate the kinetic part of your brain that helps improve learning through physical activity. I also recommend typing while you study your English grammar. This will help solidify your knowledge with movement.
As the saying goes in English: A picture is worth a thousand words. Help activate the creative side of your brain by trying to describe a photo or other image. You can combine use this also to activate your vocabulary by choosing a picture that has something to do with the subject you are going to study in English.
Next, make sure to study a number of areas rather than focusing on just one topic. Study a little grammar, then do a short listening exercise, then perhaps read an article on the same topic. Don't do too much, twenty minutes on three different types of exercises is plenty!