Seconded, but keep in mind that, for the majority of boards, you need to avoid saying anything that implies even very loosely that you might be liberal (regardless of whether you are), to keep the noise down.

You also need to have a halfway decent bullshit/unfounded-confidence detector when reading replies. This was less necessary a decade ago (in terms of the nature of replies to questions, obviously not in terms of posts in general).

Yes, though keep which board your question should go to in mind. Most of the horror stories you read about 4chan are about /b/ and /pol/. The other boards are tamer in comparison, though still not for the faint of heart.