The p of Spanish is pronounced much like the "p" of English, although it is often softer or less explosive.
If you listen carefully, you may notice that the "p" in "pot" is pronounced with a bigger puff of air, or is more explosive, than the "p" of "spot." The p is Spanish is usually more like the "p" in "spot."
You can hear the p pronounced by native speakers in our brief audio lesson on pronouncing the p. Phrases and words spoken are con permiso, preposición and proposición.
The p is silent in a few words of Greek origin that start with ps- such as psicología (psychology). Nearly all such words have English cognates. Such words are frequently spelled without the p, as in sicología.