There are so many ways to practice, but often so little time to do it. Here is one practical approach to practicing.

• Make sure you have a time and place set aside to practice, preferably free from distractions (i.e. pets, other siblings, food, tv or other electronic devices, etc.). If you don't have a plan to actually do the work, it won't happen. Consistent practice yields better results than marathon sessions (practicing in one big clump) ever will.
• Use a timer or watch the clock a little to divide your practice time. If you practice consistently, you really won't need to practice absolutely everything in every practice session. Break up your time logically. For example, if you have 30 minutes to practice, spend 5 minutes on scales, 5 minutes on exercises and etudes, and 20 minutes on your repertoire (piece or pieces you're working on). By working this way, you warm up your fingers and ears with your scales, chip away at the etude that is helping you develop or hone a certain technique, and then you get plenty of time to work on your piece(s). 
• Set goals for what you would like to accomplish in your practice session. For example, you have 16 new measures to learn in your piece. You could break that up into four sets of four measures that you can focus on separately for four days and then you can put them all together in week's remaining days.
• Look at your new music in terms of layers. Instead of trying to get the notes, rhythm, bowings, dynamics, phrasing, articulation, and all your posture and bow hold concerns correct all at once, separate them into layers. First get the notes, then, when you feel comfortable with that, play the notes slowly with a metronome to make sure you're getting the rhythm right. After that layer, add the bowings and then keep adding all the other elements in a logical order. You may find that simplifying like this will improve your accuracy and give you an opportunity to find more ways to be expressive.
• Write down in your notebook what you worked on and for how long each day. This will help you become more accountable to me as your teacher and to yourself

There are so many other things you could consider as you look to improve your practicing and, therefore, your practicing. On the "Student Center" page on this website you can find a list with additional ideas.

One of the most important skills to develop is that of learning to tune, especially your open strings because they are the foundation for all the other notes to be in tune. When I teach this skill I guess I do it the "hard way" because it is the best in the long run. I use my tuner to produce the desired pitch - the note I'm tuning to - and adjust my string to match it. By doing it this way, I force my ears to listen to whether I am too low, too high, or just right. Sometimes it is hard to tell which way to adjust the string, but, if I sing or hum the note, it becomes more clear. When you learn to tune by listening instead of just having a tuner tell you which way and how far you are off, you strengthen your ability to tell if and when other notes you are playing are in or out of tune too. 
Eventually, string players are expected to tune their instruments "by 5ths". When you do this you only receive one pitch - A - by which you tune that string and then you tune D by listening to the quality of the interval (space/distance between notes). Your D string will be in tune when the A and D together form a perfect 5th. You then tune the rest of your strings the same way, as all the strings that neighbor each other are a 5th apart.
Learning to tune by listening takes time and practice, but it pays off for both the performer and their audience! 
A good process to use in tuning would be:
1. Listen to the note for a moment.
2. Hum or sing the note to internalize it.
3. Tune the string, continuing to listen so you can match the pitch correctly.

Remember, when using the fine tuners, turning them "clockwise" will make the pitch go up (or more sharp) and turning them "counter-clockwise" will make the pitch go down (or more flat). When using the pegs, turning the upwards or toward the scroll will make the pitch go up and turning them down or toward the fingerboard will make the pitch go down.