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 hitOr 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 throwRicher than that which four successive kingsIn Denmark’s crown have worn.
Shakespeare gives advance warning to the audience about the complexity of Claudius' plan. If the fencing scene were to occur without any of the additional information, the only suspense would be "who will be hurt"? However, adding the poisoned tip and the poisoned cup add more drama to the scene and offer more possible outcomes, which increases the suspense.
I also believe Shakespeare creates suspense during the fencing match by having Hamlet strike the first and second hits. It seems possible that Hamlet, as he had alluded to Horatio just beforehand, had indeed been practising and now feels confident in his ability to beat Laertes. We, as readers, begin to think that Laertes and Claudius' plan may be foiled (pardon the pun)...but then again, it is a Shakespearean tragedy...