You can use a convenient online legal service site such as legal zoom. These online legal services will be able to help you register in any of the 50 states, and you will also be able to file taxes and annual reports through them. The services fees will vary by state.

If you are considering converting your LLC to a C-corporation or S-corporation, it is recommended that you consider Delaware. Else, if you just want an LLC, your home state is fine. You can also consider Texas, Wyoming, Nevada, Washington, and South Dakota, which have no state corporate income taxes.