I agree with Laura's recommendations.

I've been involved in ECommerce for over 13+ years and only recently, I decided to start consulting part-time to test the waters. I must say that it's a learning process (but it's fun!). I had the same questions you have currently. The way I started is pretty simple: for my rates, I simply charged close enough to what I'm currently getting paid at my job. From there, I targeted clients whom I feel I can truly help within my industry. But in regards to focusing on a specific expertise, I'm still playing with that. I recommend you start helping all sorts of clients and from there you will be able to know which type of clientele you want to work with and the type of skill you excel at.

I've joined many blogs that talk about consulting, joined many Facebook groups/forums where potential clients are interacting and started helping them. I reached out to many conferences and offered myself as a speaker. I am getting my name out and I can truly say it's actually working (I'm still learning too). It's not easy but all u can tell you is just start and you will adjust when needed. I keep changing my rates & services every month.

Hope this helps. We can certainly talk more about the details within my consulting journey :)

Cheers!