Both are prepositions "To" express a direction, a distance, expressions of time, expressing indirect object, in relation to, purpose or result... for" indicating destination, intention, purpose, on behalf of, representing, because of, with regard for, in exchange for, in favour of, refering also to a distance, refering to time, clause to an infinitive, in spite of... I think sometimes it is confusing, the only way you can is to listen the native speaker and remember it.

to = a preposition Examples from www.thefreedictionary.com a. In a direction toward so as to reach: went to the city. b. Towards: turned to me. 2. a. Reaching as far as: The ocean water was clear all the way to the bottom. b. To the extent or degree of: loved him to distraction. c. With the resultant condition of: nursed her back to health. 3. Toward a given state: helping minority women to economic equality. 4. In contact with; against: their faces pressed to the windows. 5. In front of: stood face to face. 6. Used to indicate appropriation or possession: looked for the top to the jar. 7. Concerning; regarding: waiting for an answer to my letter. 8. In a particular relationship with: The brook runs parallel to the road. 9. As an accompaniment or a complement of: danced to the tune. 10. Composing; constituting: two cups to a pint. 11. In accord with: job responsibilities suited to her abilities. 12. As compared with: a book superior to his others. 13. a. Before: The time is ten to five. b. Up till; until: worked from nine to five. 14. a. For the purpose of: went out to lunch. b. In honor of: a toast to the queen. 15. a. Used before a verb to indicate the infinitive: I'd like to go. b. Used alone when the infinitive is understood: Go if you want to. 16. a. Used to indicate the relationship of a verb with its complement: refer to a dictionary; refer me to a dictionary. b. Used with a reflexive pronoun to indicate exclusivity or separateness: had the plane to ourselves. to = an adverb. Examples 1. In one direction; toward a person or thing: owls with feathers wrong end to. 2. Into a shut or closed position: pushed the door to. 3. Into a state of consciousness: The patient came to. 4. Into a state of action or attentiveness: sat down for lunch and fell to. 5. Nautical Into the wind.

for = a preposition. Examples from www.thefreedictionary.com a. Used to indicate the object, aim, or purpose of an action or activity: trained for the ministry; put the house up for sale; plans to run for senator. b. Used to indicate a destination: headed off for town. 2. Used to indicate the object of a desire, intention, or perception: had a nose for news; eager for success. 3. a. Used to indicate the recipient or beneficiary of an action: prepared lunch for us. b. On behalf of: spoke for all the members. c. In favor of: Were they for or against the proposal? d. In place of: a substitute for eggs. 4. a. Used to indicate equivalence or equality: paid ten dollars for a ticket; repeated the conversation word for word. b. Used to indicate correlation or correspondence: took two steps back for every step forward. 5. a. Used to indicate amount, extent, or duration: a bill for five dollars; walked for miles; stood in line for an hour. b. Used to indicate a specific time: had an appointment for two o'clock. c. Used to indicate a number of attempts: shot three for four from the foul line. 6. a. As being: take for granted; mistook me for the librarian. b. Used to indicate an actual or implied listing or choosing: For one thing, we can't afford it. 7. As a result of; because of: jumped for joy. 8. Used to indicate appropriateness or suitability: It will be for the judge to decide. 9. Notwithstanding; despite: For all the problems, it was a valuable experience. 10. a. As regards; concerning: a stickler for neatness. b. Considering the nature or usual character of: was spry for his advanced age. c. In honor of: named for her grandmother. For can also be used as a conjunction, meaning because or since.