The Boston Globe's Greg Bedard has ever so kindly laid out the official rules for the NFL's new 'legal tampering' period of three days, in which teams are allowed to contact and negotiate with other teams' free agent representation. Per Bedard, the 88-hour period starts at midnight Eastern Time on Saturday (so, Friday night) and ends at 3:59 EST on Tuesday. Teams are only allowed to contact the player's agents to enter into negotiations - no contact with players is permissible during this time. While you're allowed to work out the language particulars of a deal, if you like, no contracts can technically be fully executed until free agency starts at 4 p.m. on Tuesday.
Further, no player visits can be lined up until free agency starts at 4 p.m. Tuesday, and this new 'legal tampering' period only applies to the unrestricted free agent group - restricted free agents and franchise players don't apply. As Adam Caplan noted on Twitter, this could mean that you should mark your calendars for 1PM PST on Tuesday because there may be a deluge of new deal announcements being made.