One strategy I've heard of is, like Brandon wrote, one LLC per so much in equity or property value. So, maybe 3-5 in an LLC until they reach your threshold, then start another LLC, etc. And it's important these LLCs are in the same state as your properties. Then, have a limited partnership own the LLCs and make that your operating company. You pay all bills and take your personal distributions from the LP. This still allows you to have one tax return because everything will ultimately flow through to your personal tax return, but provides for better asset protection.
As you know, LLC means "limited liability company" (limited liability is in the name) and most of the time they are disregarded entities for tax purposes. However, this can (not necessarily based on how it was set up, but could) result in limited protection. The same thing that gets accountants excited makes lawyers nervous, which is why I believe you need both in your corner working together.
Check out the Asset Protection Counsel. Depending on your net worth and other assets, they could be well worth your time. I'm not affiliated with them, but I was a practicing attorney in another life, so I do understand what they're talking about, and the limits to protection and LLC provides, and how some here might rely on the LLC a bit too much. It's just important to understand the benefits and potential limits to anything you do.