What means does Shakespeare use to raise suspense during the fencing match?
William Shakespeare builds suspense by having Hamlet refuse to drink from the poisoned cup even when he's won points on Laertes and is supposed to drink. The audience gets more and more on edge as they wait for him to be poisoned from one source or another while he refuses to drink and avoids the blade.
The biggest source of suspense is the poison. The audience knows the cup and blade are both poisoned but not when—or who—will end up actually receiving it. Since Laertes is the better fencer, Hamlet gets three chances to strike Laertes. This actually means that there are more rounds for Laertes' blade to poison Hamlet. In case that doesn't work, though, Claudius also plans to poison his goblet. He says:
If Hamlet give the first or second hit
Or quit in answer of the third exchange,
Let all the battlements their ordnance fire!
The king shall drink to Hamlet’s better breath,
And in the cup an union shall he throw
Richer than that which four successive kings
In Denmark’s crown have worn.
The audience is in suspense wondering how Hamlet will be poisoned or whether someone else will get one of the fatal poisons. However, Shakespeare makes it even more suspenseful when he has Hamlet refuse the poisoned goblet after making a hit on Laertes. He says just to wait until they're done.
drinks the poison and the poisoned sword strikes both Laertes and Hamlet. Claudius, of course, is both struck by Hamlet with the poisoned blade and forced to drink the rest of the poison.