Hi
When I start to write a short story I have the POV uncosciously decided along with the rest of the necessary elements. Some stories work better in first person, especially if you are trying to create tension, suspense and empathy in the reader. Others where muliple characters feature are best told in third person. Occasionally I will even tacke 2nd person which is an intensely poweful way to write.
There are pros and cons for each differing POV and I basically let the story decide which POV fits best.
To explain to anyone who isn't sure.
1st Person = Writing as a character "I, Me, My"
2nd Person = Writing to a character as a narrator "You"
3rd Person = Writing as an omnipresent eye. "They, He, She"