Wohlfahrt's Studies opus 45 are a must for the early stages of violin playing.
Together with the etudes of Dancla and Mazas, they provide excellent preparatory material for the more difficult studies by Kayser and Kreutzer.
Wohlfahrt's Foreword to Opus 45 :
The study of the violin presents particular difficulties for beginners which are often the cause of a sudden drop in the pupil's enthousiasm and ambition, even before he has mastered the first rudiments. The blame for this situation is frequently laid on the teacher, who is labelled incapable or negligent, without considering the fact that the pupil began his studies without the slightest notion not only of the difficulties to be encountered, but also of the regular and assiduous practice time indispensable for surmounting them. It is thus important to smooth these first asperities by showing their utility and making them agreeable; to this end my Violin Method was published and the present Exercises have been written, which latter may be considered as forming a supplement to the former. If practised with care and intelligence, they will serve as a solid foundation for the technique of any player ambitious to become an artist.
General technical remarks for Wohlfahrt's Opus 45 :
Studies written in detache bowing (such as nos. 1, 2 and 3) should be practiced also with a great variety of bowing patterns in the aim of developing bowing technique
The left hand should be kept thoroughly relaxed, with the fingers very close to the fingerboard. In particular, the fourth finger should always remain above the strings
The first finger acts as an anchor for the entire left hand, and should thus be left on the strings as much as possible
The use of open strings is to be encouraged for beginners, as they provide an excellent reference for intonation and have a pleasant and pure resonance