Month to month, at least 30 day notice, and you should expect to pay a higher monthly rent vs. that with a 6 - 12 month lease.
edit: it is probably determined by laws in your state, but I would specifically find out if 30 day notice is as of day landlord receives official notice, or at least 30 days after next first of the month (I suspect first, but am not sure). And you should find out what penalty for breaking a 6 month lease is then weigh cost of each option based upon best educated guess of how many months you are likely to be away.