Pretty much the same tactics i am using to beat the top 3.
I am amazed at some these questions that seem to defy logic. It is not uncommon for top players to lose matches to other top 20-30 players. [Great Federer and Great Sampras lost matches, if so called greatest players can lose matches, i am sure others will ]
In order to beat these players, one needs more than strategy. One has to play execptionally well , take every chance and then also hope that the other player is a little off that day.
As far as i know, the only strategy that Federer couldnt successfully overcome was the Nadal's "hit to federer's backhand " strategy. So many people tried to go after federer's backhand over the years but only Nadal was successful.
Other people that beat Federer, followed a different strategy that suits their game.
Same case with Nadal and others.
Against Murray, all one has to do is set the match in England!