Attention! Some basic rules must be followed. For example:
keep your back aligned to prevent back problems in the long term;
keep your shoulders aligned, for the same reason.
To play acounstic popular guitar uses traditionally
right leg as support for the musical instrument,
but you can see below, the illustrations that show
two ways to support the guitar on your lap (left or right)

Violao de Seis Cordas Violao de Seis Cordas

Note: Traditionally the 'right support' is used in 'popular guitar' or 'folk guitar'
and the 'left support' for the practice of 'classical guitar' or 'classic'.
However, the mos important is comfort for the guitar player,
both can be used to study acoustic guitar.