My microphone keeps clipping whenever I say P's, T's, and S's. How can I fix this?

Those types of consonants that require a strong release of air and the higher pressure levels are called plosives and can cause the microphone to peak.  To eliminate those problems a pop-filter, like the Samson PS01 or PS04, can be placed in front of the microphone and will absorb the initial burst of air, and pass only clean audio through to the microphone.  Turning the microphone slightly off-axis from your mouth can also help limit the peaks.