I want to start a online review site; what are the best ways to protect my self legally should I form an LLC or trademark or both?

Totally different things, serving different purposes. A trademark protects a "mark"--a work, a phrase, a name, an image--associated with your business. (Technically, products are protected by trademarks, businesses by service marks, but we don't need to get into that distinction here.) It prevents others from trying to confuse your potential customers or steal your business or reputation--if you have trademarked your product, in this case, your review site, others cannot use that name for their own businesses. So a trademark will protect your customer good will; the investment you make in establishing yourself.

An LLC is a limited liability company. Having an LLC means that you--your personal assets, and your income from other sources--are insulated or protected from debts or liabilty incurred by the LLC. (For example, say the LLC violates someone else's copyright, or defaults on rent; in either case, the LLC can be sued, but not you personally.) So the LLC protects YOU, not your business.

You should do both: set up an LLC to protect yourself from liability, and if you have a name for your site that you want to protect, trademark. And get insurance, too--that's the third, and very important way, to protect your interests.