1. Who do you turn to? 2. Whom do you turn to? 3. To whom do you turn?
#1 is what you will hear most of the time. The use of the object case of the pronoun "who" is declining. It is a sign of the evolution of the language which has been losing inflections, subjunctive verb forms, and strong (irregular) verbs for centuries.
1. Who do you turn to?-- Now accepted in informal English 2. Whom do you turn to?-- Now usually pooh-poohed as mixed register, used by someone trying to be formal with 'whom' while retaining the informal terminal preposition. 3. To whom do you turn?-- Still accepted in formal English