I did pretty well on the PSAT, but I'm still a little nervous about the real SAT. Will it be significantly harder than the PSAT? What concepts and types of questions will I see on the SAT that weren't on the PSAT?
Overall, the SAT is very similar to the PSAT in the material it covers. It's just a slightly longer test. The Writing section is actually identical in length and content to the PSAT (both have 44 questions). The Reading and Math sections on the SAT are longer than their corresponding sections on the PSAT, but only by a few questions. The Reading section has 52 questions as compared to the PSAT's 47, and the Math section has 58 questions as compared to the PSAT's 48.
You'll see a few more questions about certain Math topics on the SAT, but these topics still show up on the PSAT. For example, the SAT has 6 questions that deal with the "Additional Topics in Math" content area, while the PSAT only has 2. This means that for the SAT, it's slightly more important to brush up on trigonometric concepts.
Your PSAT results should be a fairly accurate prediction of how you'll do on the SAT. Even though the stakes are higher for the SAT, it's not a whole lot different in what it covers. You can check out more detailed comparisons between the different sections of the two tests on the College Board site.