I practice every day, sometimes 20 minutes, sometimes 2 hours.
I'm not doing a specific method but I have the Suzuki books, which are great. I started out doing the first song at my first lesson, but I skipped* some songs because they ended up being too easy, so I've moved up and am now on the 8th song of the first Suzuki book and am currently working on my fourth finger. I started 5 weeks ago.
I do it as a hobby, I love music!
Exercises: since I only know first position, I do scales in one octaves but can do G in two since it starts on the first open string. I also do arpeggios, it's great for the fingers and building up speed.
I don't mind playing the same song over and over again because it's better to stay on one song and really know it perfectly than to keep changing, but I usually get more than one piece a week anyway so I'm never really bored.
*not really skipping per se, but learning extra songs in my spare time and showing the teacher that I am capable of playing them so that she didn't have to go over it with me in class.
I haven't really played for the past two years, but when I was playing as a hobby before then, I'd practice basically every day, 40 minutes-two hours in a session. Usually just one session a day, but if I was really feeling it, sometimes I'd practice twice a day. The best practice is the one that focuses on what you need at the time. Even for one person, that can change frequently. Some days, I may need to really polish my scales, maybe next week I'd have to work on my fifth/sixth/higher positions. I did use Suzuki very frequently for warm-ups; I'm not sure I'd use them so much now, but I still keep them around because sometimes it's good to go over stuff you learned long ago.
When I had orchestra concerts coming up, I tried to do practice sessions that were twice as long as what the concert would be. That way, I built up endurance, so the concert wouldn't seem so long to me.
And yes, repetition. Practicing for orchestra, I'd put on a CD and play with it over and over and over again until I basically memorized the music.
That being said, keep in mind that practice does not make perfect. Practice makes permanent, so if you're repeatedly playing something incorrectly, you'll learn it that way and it'll be very difficult to unlearn later.
And not a violinist, but from a more professional perspective, my dad plays horn in two orchestras, various horn clubs/societies/chamber groups, and freelance work. He can easily practice 4 hours a day (maybe not all in one sitting) when he's got something he's practicing for, rather than just keeping in shape. I'm sure he'd practice more if he could but being in so many groups cuts into his practice time a bit! :p And there does come a certain point when you're just too tired to get anything out of practicing.
It all depends on why I'm practicing and how much time I have.
When I practice for fun, I do a lot of playing through of pieces that I've already worked on, stopping here and there to do some detail work, but largely just running through start-to-finish. Depending on how it goes, I may make notes in my practice journal of things to come back and clean up or improve (the double stops in the first movement of the Mendelssohn concerto have a permanent spot on the list...). Most of my orchestral pieces are 'practice for fun' pieces, as I get more out of practicing in rehearsal with all the other components to the piece happening around me. I'll sometimes work on a tricky orchestral section during 'fun' practice.
For quick-and-dirty, no-time practice sessions, I do a lot of work on scales and a little bit of work on melodious etudes / caprices (i.e. Kreutzer, Dont, Rode, Pagannini). Scales and scale-based exercises give a lot of bang for your practice time -- the simplicity of scales give you a great opportunity to work on some very specific bowing technique targets while still doing good pitch and fingering practice. So many scalar patterns exist in concert repertoire that spending a lot of time on scales will improve almost all aspects of your playing. The etudes are an opportunity to get in some more holistic practice and to keep me from getting so bored that I want to stab out my eyes with my bow. :)
If I have specific goals or I'm taking lessons at the time, I work through a series of scales, technical exercises etudes, art pieces and concerti. I spend about 50% of my time on scales and technical exercises, regardless of how much time I have available. I rotate through scales and scale systems, using the Carl Flesch book as well as the William Primrose concept of practicing finger distribution patterns in each key and position on each string. I work on technical exercises from Sevcik, Schradieck, and the Simon Fisher Basics book according to what needs to be improved in my performance (using my practice journal as a guide to what to pick) as well as working on expanding and refining my technique. I also create technical exercises of my pieces by working on very specific, targeted areas with a very specific goal (example: in solo Bach, I will work through a movement going pitch-by-pitch, just focusing on intonation. I might then pick out a few trickier sequences to work on for accuracy and speed, superimposing a different rhythm to mix things up a bit but still working specifically on accurate intonation). Most of my work on my concert pieces is unrecognizable to someone not intimately familiar with the piece -- a lot of slow, thoughtful playing to make sure that I'm learning it the way I want to perform it. I've learned that slow practice on the front end of the piece reduces the amount of time it takes for a piece to be learned the way I want to perform it. I keep it from being boring by setting a timer and working on one goal on one section for only a few minutes at a time in any given practice session (but I may repeat that same section several times to work on several goals -- intonation, rhythmic accuracy, vibrato and tone color, bow distribution, shifts...).
I find keeping a practice journal really helps keep me focused, especially when I'm doing a LOT of practice. When I was in school, I was practicing 3-4 hours per day. I have significantly less practice time these days, so it's even more important to be focused and targeted when I do have time to play. I have carpal tunnel issues, so I tend to break practice up into several one- to two-hour sessions with breaks every fifteen or twenty minutes to allow my hands to rest. I also take anti-inflammatories round the clock when I'm doing a lot of playing.
My background: I currently teach middle school instrumental music (winds and strings). I play as a semi-pro with a local symphony as well as gig for shows and one-off concerts (such as filling in as an extra for colleges with smaller music programs). I have taught beginners through intermediate students. I play violin and viola at a high level, and am considering applying for a performance graduate program within the next five years.
Hope that helps!
When I was preparing for undergraduate auditions and when I was a music major, I was practicing 4-5 hours per day. My sessions usually began with 10 minutes of muscle warm ups. Literally stretching and doing LONG bow strokes with slow vibrato. I would go into scales and arpeggios at varying speeds/ bow combos, do etudes, and then practice any solo piece or orchestral music we were working on. Honestly, each session has a different goal. You can't just be like, "yup, playing through all this today!" Usually, I would pick 2 lines I was struggling with or even a transition between two notes. I would start at the lowest metronome setting and slowly work myself up to going FASTER than what I was supposed to. It's very effective practice, although extremely tedious.
It goes without that I do NOT practice that way any more. I am lucky these days to have my schedule open in such a way that I can play in the community orchestra in my town. But, being a teacher and wanting to go to med school cramp my violin style. But, when I am in an orchestra, I practice the same way. Not for 4 hours, but I use the same techniques.
I think that practicing should help you grow and it shouldn't feel like a chore. Some people few it as such. I think that if you see practicing as something that not only makes you a better violinist, but also a more diligent and persistent person, you'll get a lot more out of your "intimate" time with your instrument. :-)