If you have a question about the forums, you can ask it in the Forum support & feedback forum.
If you want to point the attention of a staff member on a certain post (because you believe it's fluff, spam, in the wrong forum, etc) then you can use the little red report flag button that you'll find to the left of each post.
If you have a question that only a staff member can answer and you don't want the whole world to see, then you can send a PM. Do read the FAQs about PM's: http://www.sitepoint.com/forums/faq.php?faq=messaging#faq_pms
All other questions are best posted in the suitable forum, where all members (staff and non) can join the discussion and contribute to the answers. There are a lot of great non-staff members here that answer questions.