Establishing residency in a state, or non-residency where you have/had residency before can be different for each state. Additionally, it depends on what you want to establish residency for. For example, residency requirements in a state for reduced tuition at a state collage may be totally different from residency requirements for voting in that state, which can be totally different from residency requirements for declaring the state your "tax home" for state tax purposes.
For example, in FL a northerner who owns/rents property here and only lives in FL for the winter months, can establish their residency by filling out a form and filing it with the local registrar in the county courthouse of the county they live in. Even then, that may not be sufficient to "cancel" their residency in whatever state they came from.
