Definition of Tapping Up:
A milder form of "tapping up" involves a manager's letting his admiration for a player at another club become known, perhaps by hinting at his interest while working as a pundit during the broadcast of a game in which the player is taking part, "he's the sort of player any manager would be very keen to sign", or by lavishing praise in programme notes when the two teams meet. There are also the "source close to the manager"-type newspaper rumours which in many case originate within the club and are intended to flag an interest while retaining plausible deniability against charges of tapping up. Most ex-players candidly admit that tapping up has gone on in football for decades. Nottingham Forest manager Brian Clough later said, "we tapped more players than the Severn-Trent water board!"
Notorious examples of tapping up in the Premier League include Dwight Yorke and Ashley Cole. In these cases, the incidents soured the relationship between the player and his original club. Cole was found guilty and fined £100,000 by the Premier League on 2 June 2005 for a meeting in a hotel in January 2005 between himself, the Chelsea manager José Mourinho, Chelsea chief executive, Peter Kenyon, and his agent Jonathan Barnett.
Chelsea were again at the centre of a controversy in 2009, when the club was found guilty of inducing Gaël Kakuta to break his contract with French team RC Lens in 2007. As punishment, they were banned by FIFA from registering new players for two transfer windows.[3]. Just when Chelsea got out of their transfer ban, they were then in the midst of another controversial episode of possibly unsettling/tapping up Fernando Torres from Liverpool who mysteriously put in a transfer request a couple of days before the January 2011 transfer window shut. Harry Redknapp, manager of Tottenham Hotspur, has said that activity which verges upon 'tapping-up' regularly occurs in deals between Premier League clubs, and Scott Minto, a pundit for Sky Sports, said that the ban was "extremely harsh" because of the frequency of it. However, there have been other cases where clubs have received transfer window bans for tapping-up; notably, Roma over Philippe Mexès, and FC Sion over Essam El-Hadary.
Funniest quote out of all of that was Cloughie and his honesty, tapping up is when club officials discuss a transfer without the other clubs consent. Problem in determining this in modern football is the amount of agents/money swirling around obviously the first contact with clubs buying players will be through agents not other club officials but if you could tap people up just by player-player banter then Spurs would sign half the Dutch national team and Barce would sign Torres, Alonso, Fabregas, Ramos etc. It will have an impact but they are supposed to be professional footballers so the factor of being with your friend every day can not be that big a factor in a players decision.
Back up the above Newcastle story, just saw it come on the ESPN news feed (VERY reliable source <3)
http://soccernet.espn.go.com/news/story/_/id/923223/newcastle-up-bid-for-lorient-striker-kevin-gameiro-to-L10m?campaign=rss&source=soccernet&cc=5739