When you feel very relaxed in your whole body and specially in you right arm (using bow) and you're prducing a solid and a bueatiful tone, then you're doing it right. But how do I do this? There are so many ways, that's what you have to know. There is no one way and what may work for one person might not be as good for another. But the basic is, relax the whole arm and let it literally hang on the bow so this weight is the only pressure making the string move. If you don't get a quick responce from the string you can add a little and a mean a LITTLE pressure with your index finger. Your fingers and wrist must be flexible in bowchanges, if not you will always get an accent when changing bow. Holding the bow, try both placing the thumb on the wood and in the frog. When I started I had mine on the wood but now I feel I can control the bow better with my thumb in the frog. Good handposition is important for the left hand, I recomend Streicher (you dont need a teacher, just read the forword and the beginning of book 1) for the lower register, and Petracci and Streicher together work good for shifts and thumbposition. Check out as many etudes as you find but before working on an etude you must decide or find out what you have to learn from it and then practise it with that in mind. Be critical and listen to your string crossing, bowchanging, intonation ect. and always start a new etude playing it at least, and I mean at LEAST half tempo so you can listen to what you're doing. Changing string=wrist movement, minimum movement of arm playing very fast detache = wrist is the only moving part of your body, everething else is relaxing. Ok, maybe your left hand will be working hard...sorry! If you tired and not paying attention to what your doing then stop practising, you're not making progress if the brain isn't working. Good technique is all in the brain, it's the brain who makes all the decisions. 2 hours of hard concentrated practising is better than 8 hours of playing without thinking. I can't write more now, I'm to tired to think.