Assuming we are in the martial arts to learn, it would be good to learn as much as possible as often as possible. Here are a few ways to keep the information flowing in.
1. Keep a Beginner's Mind:
This is sometimes called "Shoshin", it means to stay in that open, uncritical, spongelike state that you had when you first started the arts, or when you first started life for that matter. Just take it all in and file it away. Contrary to common opinion the brain doesn't fill up to a certain point and then start dumping stuff out the back end as new stuff comes in the front. Some people seem to put up barriers to information as they get older, try to resist that urge. You really can keep accumulating new ideas, so let yourself do it.
2. Watch carefully:
The martial arts are physical, they are expressed physically, and are learned physically. The deeper ideas are taught physically so when you see your instructor or anyone else performing the arts, watch them. Watch without comment to yourself or to others, just absorb what you are seeing and try to feel it in your own bones. When your teachers demonstrate a technique they aren't just showing off their skills, they're explaining things, listen with your eyes.
3. Listen carefully:
On the occasions when your teachers do stop and talk to you, listen very carefully. Don't rationalize about what you're hearing, instead just accept that your instructor is trying to transfer knowledge via another channel. If you ask questions in your own head or say "I know" you'll slam the door shut. Most sensei don't really talk to hear their own voice, they are trying to pass something on, so don't be afraid to ask for further explanation once in a while, just don't ask questions that reveal that you were thinking of something else. Few people like talking to themselves, especially if they're asked to repeat it to themselves several times.
If your instructor is talking directly to someone else, listen. Do you really think that you aren't making that exact same mistake? If you listen when the guy next to you is corrected, and then correct yourself, your teacher may even smile at you. Rare joy indeed.
Class time usually includes practice time but that isn't enough. Your instructors like to see you improve and if the entire class is spent getting you back to the same skill level you left with last week, it's all a waste of time. Don't be afraid that you will "acquire bad habits" if you practice on your own. It's a very poor student who can't change a habit, after all a habit is just something that people who don't want to learn, do to fill in their days.
Practice on your own time, and try to correct yourself. Don't rely on your teachers to do your learning for you, they will eventually get tired of telling you to change the same thing over and over again. Change it on your own time so that you can get on to the next step.
If you can't get the time, space or equipment to physically practice, visualize your practice whenever you have a quiet moment or two. Go through the techniques in your head and try to feel them in your body as you do it. This will also help you to learn how to watch correctly. If you can see someone do a technique, then close your eyes and see it again while you feel it in your bones you'll be able to "steal" skills from anyone.
Despite what many people believe, you can learn from books, all you need to do is pretend that you aren't seeing words on a page, but that you are hearing your teacher say them to you. When you look at an illustration or a video pretend that you are looking at your instructor. Now the book isn't so different from sitting in class and watching is it? Best of all, you can ask your "book instructor" to repeat that last move as often as you wish.
7. Visit other instructors:
Part of the objection to books is that they usually aren't written by "your" instructor. Even worse for some people is the idea of looking at another instructor for fear that you will "learn bad habits". Those habits again, you'd think human beings were "write once-read many" programmable computer chips. A good teacher will tell and show you the same thing over and over from as many different angles as he or she can think to tell you, in an attempt to get you to understand a movement. Sometimes though, students just get blind and deaf to one teacher and hearing it from somebody else will work. The more ways you can look at a problem, the less of a problem it becomes.
8. Cross train:
Practice other, similar art forms when you get the chance, but even more, do other types of exercise entirely. The arts are repetitive, and practicing the same motion over and over can cause muscle fatigue and soreness from that motion which may actually reduce your ability to learn the correct movement. Practicing other arts which are in the same "family" as yours will let you work on common aspects of the arts while giving your joints and muscles a rest from the specific movements. Similarly, going for a run or lifting weights or doing some other physical activity will increase your overall fitness while allowing different movements to gently work your "martial muscles" out of spasm and fatigue.
Rest, eat, recuperate. Weightlifters know that you can't lift every day, day after day, and expect to improve. The same is true of learning a skill, you have to give your mind and body a chance to absorb what you've accomplished, and to incorporate it into your overall way of thinking and moving.
10. When all else fails, teach:
Sooner or later you may find yourself without
an instructor, in that case you might consider teaching as a way of continuing
to learn. By looking at students and seeing what "habits" they pick up
you are looking into a mirror of your own practice. By finding a way to
transmit a movement, you reinforce it in yourself. By listening to questions
and finding the answers you deepen your own knowledge. If you truly attempt
to make your students as skillful as you can, you will find that you must
be brutally honest about your own skills, and that can teach you more than
any master ever could.