Tips for effective practicing.
Practice a little bit every day.
Waiting for one day to practice for two hours will not make you better, just tired.
Practice as soon after a lesson as possible.
Any new skills or materials you learned in your lesson will be reinforced more strongly the sooner you review them. The longer you put off practicing, the more you will forget, up to the point that your next lesson could be like starting from scratch!
Use your brain while practicing.
Don't just go over exercises and pieces once or a few times and declare yourself done. Try to remember what your teacher has said about a particular rhythm or finger placement, or your bow or your posture. Keeping these in mind will be like having a lesson every time you practice.
Play sections of pieces rather than play from beginning to end. Start sometimes in the middle so that the middle will be as good as the beginning. Go over just the hard part--that's how it gets easier. Many times, a difficult passage is only due to 2 or 3 notes. Find them, smooth them out, and you'll find that the whole piece works better.
Repeat, Repeat, Repeat.
Once you have something worked out, play it several times so it becomes automatic. But be CAREFUL not to repeat a mistake, and don't let the mistake be the last thing you play. Another reason not to wait too long to practice after a lesson--you may forget how something is supposed to go and get used to practicing it wrong. Then it's hard to unlearn.
Finish with something fun.
Try to save your favorite piece for last. Think of it as 'dessert.' Work really hard on the skills and learning pieces, then enjoy your hard work and your instrument on something you just like to play. Then share it with someone else (like your parental units)!
Scales for beginners: