How long should you remain at a job before looking for another?

Tell your boss the truth. They are most acceptable to you leaving if they know the real reason (especially in this case). I would give the boss about a moth's notice and then put in a 2 week notice when it is time. Don't tell people that you are leaving as they may start turning on you. I would wait to tell everyone (with the exception of the boss) untill you put your official 2 week in, so your boss has plenty of time to interview and potentialy have you to help train the new person.

Good Luck!

Since this is your first job out of college, is it the whole newness thing that's got you thinking about moving closer to friends and family? Have you found difficulty getting yourself established socially in your new location? I'd try to stick it out at least a year if at all possible. What are your currently living arrangements? Are you leasing? Maybe wait till that's near the end of it's term.

Do what is best for you whenever it's best for you to do it! Don't tell your boss til you have another job lined up and are ready to give two weeks notice! If you say anything to anyone, it will get out and they may let you go before you are ready! ALWAYS do what is in your best interest, not the job's! They wouldn't hesitate to let you go if it was in their best interest!!!