"To choose one's dog"
Translation:Choisir son chien
Well it would be better if you pointed out what's bothering you first. The English expressions using "one" to refer as "someone, but no one in particular" usually have no equivalent in French. We can use "on" instead, but it can't be done in this particular sentence, so we don't use any pronoun.
Here is an example for each situation :
- "One would think it's enough, but no." = "On penserait que c'est suffisant, mais non."
- "One has to help himself quickly" = "Il faut se servir rapidement."
Yes it's not correct French, because "même" is not a noun.
Two correct alternatives to your sentence could be :
"Pour choisir son chien" = "To choose one's dog." OR "To choose his/her dog."
"Pour choisir le chien d'un <insert your noun here>" = "To choose <insert your noun here>'s dog."
For example : neighbor, man...etc