If you will be a single-member LLC (meaning you are the only owner of the LLC, which most self-employed LLC owners are), from a taxation perspective, you will be taxed as a sole-proprietor. It is a pass-through business entity, where your business revenue is your income.
From a taxation perspective, single-member is not so good due to an additional self-employment tax of ~15%. Also, if you are not disciplined enough as a person with money/budgeting, not paying quarterly taxes through out the year will result in IRS penalties. Also, when you will do your income tax, you can get a surprising (unpleasant) bill on what you owe in taxes if you have a significant revenue amount. Have to be super disciplined with your expenses tracking, so you can deduct as much as possible.
If you have the slightest intent on growing the business to a scale where you will hire employees (including yourself) and pay with W2s, definitely go for the S-Corp entity (pay salary and dividends, if you choosing to do so). With S-Corp, you will have to do your payroll, or hire a payroll company/service.
You can search online (Google or YouTube) with keywords such as "Benefits LLC vs S-Corp" or whatever. Plenty of info available.
For LLC, as mentioned above, go register the business (business name, your name, etc) at your Town Hall Center and go online to your state and register the LLC and pay the ~$500 yearly fee. You will get your EIN number a go from there. Unless this makes you extremely uncomfortable, no need to hire a company or lawyer for this.
Generally speaking, most people start with an LLC, as it is very simple to start off. Once things begin getting complicated with business growth, then you can opt with the IRS to be taxed as an S-Corp (there is an IRS form for this), or convert the LLC to an S-Corp entity.
Good luck!
