✋ How do you decide your fingerings?

I just try to find a fingering which allows me to play the piece without the technical difficulties ruining the musical flow. So I try to avoid big shifts or very awkward left hand position changes mid phrase. I suppose my goal is for the listener to hear the piece and not be aware what and where the playing issues are. The least effort I can use , while ensuring I deliver the music as written, the better.

I usually start by following recommended fingerings but don’t worry about moving away from them if I feel I can find a solution which suits my hands better.

I am a returning beginner, meaning I studied and played for 3 years, was in a car accident, suffered injuries to both hands and am now returning to "take the guitar seriously".  In the past I treated editors markings as "suggestions".  My teacher at the time was not so happy about that and felt it made me miss many of the learnings the pieces were trying to stress.  Best example, playing 'p' markings with 'i' or 'm' to avoid awkward string crossings.  These days I am following the marks to the best my hands can manage.  If I can't manage a stretch or other movement I adjust to fit the hands I have now.🙂

I have been playing classical guitar for many years. My view of fingerings is nuanced. Formal studies such as Guiliani right hand arpeggios or more didactic studies of Carcassi, I play the composers fingerings. Formal everything else I work through the piece, try the editors suggestions then write in my own. Try out open strings. I use a pencil as growing experience of the piece often makes me change my mind. If a note represents a level of playability in conflict with flow or rhythm, I debate its very inclusion especially if duplicated in a chord. My hands and fingers are mine and the editors are his. My fingerings take into account my peculiar strengths and weaknesses. Many editors are academics and rarely perform. The crucible of actual performance using fingerings which are as simple as possible means you can dedicate your efforts to expression and interpretations not showing off. 

At this stage of my learning, at best early intermediate, I will use the fingerings provided in the score I am playing.  I will, however, make changes if I run into a part that I find difficult or uncomfortable to play as written.  An exception is when I am playing a passage as a technical exercise to learn something new or to practice a particular skill.  Then I trust what has been provided.

I compare different editions to see what the editors intend musically or technically. I change the fingerings wherever I cannot play them, or where I find a musically better solution. In general, re‑fingerings help me play a passage more effectively. Ideally, I would like to have sheet music both with and without fingerings.