How to choose the instrument? - Luthier Vladimir Kalashnikov
First of all you should define your purposes. What do you need your instrument for (study at school, college, university, to work in the orchestra, solo career, etc.)?

Then you choose the age of your instrument: if you need a modern (up to 50 years) or an antique one. If you have a teacher, it is better to take into account their opinion.
The next step is the size of both the body and the scale length. It is worth trying the instruments of your colleagues or friends. Then define your financial possibilities. Do not forget, that an old or damaged instrument will require more careful treatment. It will become especially acute if you travel a lot.
During the trial of an instrument do not rely only on your own taste. The playing person and the listener hear very different sounds. You should try to play in a habitual acoustic and obligatory in a concert hall.
Comfort during playing is not less important. As well as the width and the thickness of the neck are (they can be regulated).
To make up your mind about the instrument you need about 3 to 5 days apart from the cases when you immediately dislike it. Do not judge the instrument by its appearance. The appearance can be deceptive.
And do not give up. Finding “your” instrument is not an easy process.

                    Good luck!