In Shakespeare's Richard III, what strategies does Richard use to set his plots in motion? Why are they so effective?

In Richard III, Richard uses a variety of tactics to achieve his ultimate goal, the English throne.  His tactics vary primarily according to the characters with which he interacts.  Shortly after the play opens, the reader/viewer gets a clear picture of Richard's physical appearance, specifically his physical deformity.  Richard concludes that his physical appearance tends to cast him in a negative light among those in his family and at court.  Rather than fight their perception of him, he embraces his deformity, using it as a physical representation of his psychological self.  Though he reaches this conclusion, Richard presents himself as a loyal, awkwardly charming political figure; however, his real motives are far darker.  Richard turns on this charm with specific characters, if he sees that it could work to his advantage.  This is specifically the case with Anne, the woman Richard wants to marry.  It is the common perception that Richard had Anne's future husband killed.  Anne, buying this explanation, is very hostile toward Richard's advances.  Richard, rather than forcing the issue, proceeds to charm her, suggesting that the rumors are just that, rumors.  In a very real way, he tells her what she wants to hear.  He asserts his loyalty, as well as citing that he gained little from his death.

To reach his ultimate goal, Richard has to move from his position as fifth in line for the throne to the heir apparent.  Edward IV, Clarence, Edward (young prince), and Richard (young prince) stand in Richard's way to becoming king.  While Edward becomes ill and will ultimately die of natural causes, removing the three other heirs from the line of succession requires Richard's intervention.  To effect his plans, Richard manipulates those around him, specifically those who help him carry out his plans.  They work specifically to spread misinformation, a rather passive, though effective form of intervention.  At one point, Richard has Hastings spread the rumor that the two young princes, Edward and Richard, are illegitimate and therefore should be removed from the line of succession. 

When he sees this does not work, Richard moves on to his more common method - strategic murder.  While many in his family assume Richard ordered the death of the imprisoned Clarence, Richard puts his murderous instincts to more direct use regarding the two young princes.  When the rumor that they were illegitimate proves unfruitful, Richard, after being named the protector of the princes, hires three men to have the children smothered in their beds.  After the deed is done, Richard is declared king.

Richard's motives, though ruthless, are quite simple.  He essentially lies, cheats, and backstabs his way to the English throne.  By ordering the murder of Clarence and the two young princes, Richard maintains his distance from the actual deed, thereby giving him plausible deniability.  First and foremost, however, Richard manipulates the views of those at court.  He presents himself as someone who is loyal, humble, and above suspicion - though many suspect him anyways.  Doing this lets the characters' guards down.  It is the "reasonability" of what he says that allows him to be successful -- at least for the majority of the play.