The golden rule of classical guitar right-hand technique is alternation. You must never use the same finger twice in a row for scale passages.

Move your 2nd finger to the 6th fret of the A string, and so on.

This book is available as a PDF or hardcopy, and it comes with for each exercise, making it an invaluable tool for self-taught players.

Slurs build strength in the intrinsic muscles of the left hand without relying on the right hand for volume.

The gold standard for classical guitarists is the Andrés Segovia Diatonic Major and Minor Scales system. Segovia compiled 24 major and minor keys across specific, multi-octave fingerings that minimize awkward position shifts. Managing Left-Hand Position Shifts

Strength and independence in the left hand are developed through slurs (hammer-ons and pull-offs).

Alternate m-a using free stroke to challenge the weaker fingers.