The first steps I took after creating my LLC were to obtain an EIN and create an operating agreement. An EIN will allow your business to open a bank account and begin to build its own credit history & score, separate from yours. An operating agreement simply puts down in writing how your LLC will operate, and can show a judge that you have intended to truly operate your LLC as a business.
I sent all of the official paperwork to my CPA so he could begin working on my LLC's tax return (I have a true partnership and not a single-owner LLC, so my state requires a separate tax return).
Next, I opened a business checking account. All of your income and expenses should go to and from this account. I have read that it is incredibly important to keep your business finances and your personal finances separate should you either be audited or sued in the future. Change all of your payments to and from this account.
Most recently, I requested permission from my mortgage company to deed my rental properties from my own name to my LLC. My mortgage company allows for this after 1 year of ownership, provided I send them the documentation. I had my attorney draw up the deed transfer and send it to the county records office. I also sent lease addenda to my tenants letting them know the new owner & landlord of their residence -- my LLC.
This was my specific experience, and yours could vary widely. This is not professional financial, tax, or legal advice, and I always suggest that you contact professionals in each of these areas regarding your specific situation.
All the best!