Because Patler will need the details to prove me wrong in the future, here is a fairly clear write-up of the changes courtesy Jason Wilde:

On Tuesday, the NFL expanded its practice squads from eight to 10 players, but the league also added another significant wrinkle: Teams can use the two extra spots to sign veteran players who have earned no more than two accrued seasons of free agency credit. Previously, a player who spent more than eight games in a single season on his team’s game-day active roster lost his practice-squad eligibility.

In addition, players must spend six weeks on the practice squad for it to count against the three three seasons they’re allowed to spend there. The previous requirement was just three weeks.
http://www.espnwisconsin.com/common/...5331&is_corp=1