Residency is a facts-and-circumstances question, and the burden of proof sits with the taxpayer. A new driver's license is helpful; it is not the whole record.
Before the move: establish the intent, sequence the sale of the prior residence, and confirm how income will be sourced in the transition year. For Puerto Rico Act 60, the bona fide residency requirements and the timing of the move are the entire analysis.
During the move: keep a contemporaneous day count, move the tangible evidence of your life — vehicles, memberships, professional licenses, medical relationships — and document it as you go rather than reconstructing later.
After the move: file the nonresident return for the prior state, retain the record for the years a challenge is possible, and review the structure of any business that now operates in two places.