Should I practise a scale on the fretboard from left to right, right to left, or are there a bunch of positions, like first chunk of notes is while I have my fingers spread on 4 or 5 frets, next position I have my fingers spread on the next 4 or 5 frets? This is still a mystery.
It's up to you how you'd like to practice them, you can try them starting with a different finger on the root each time, like:
Index
G l ------------------------6-7-9-7-6-------------------------
D l -------------------7-9--------------9-7-------------------
A l ----------7-9-10------------------------10-9-7----------
E l -7-9-10------------------------------------------10-9-7-
Middle
G l ----------------------6-7-9-7-6---------------------------
D l --------------5-7-9--------------9-7-5-------------------
A l ------5-7-9------------------------------9-7-5-----------
E l -7-9---------------------------------------------9-7-5-7-
Pinky
G l --------------------4-6-7-6-4---------------------------------
D l ------------4-5-7---------------7-5-4------------------------
A l ----4-5-7-------------------------------7-5-4----------------
E l -7-------------------------------------------------7-5-3-5-7-
You can do the same starting these scales on the A, D, or G string as well. Memorizing these fingerings, or "shapes" you can think of them as, helps you play in different keys easier. All of these B minor scales start on the B note, so if you are ever playing a song in E minor, all you have to do is play this fingering starting on an E note and you'll be playing in key.