Here is the process:
1) Determine your worth in the market. If you are confident in your skillset, have a solid portfolio, and experience working the market then you should charge like a lawyer. There are costs to doing business like promotions and advertising that you must make up in your billing. If you lack the confidence to start a company and bill like a lawyer then you are not ready to perform as an independent consultancy. If you charge like a professional you will be treated like a professional. If you charge like a child you will be treated like a child. If I were a freelance business agent I would charge $150 per hour for my time, which is a fairly standard rate for external business services in many different fields. If you are a programmer or database architect you get to charge more. You have to remember as a free agent you have no 401K, health insurance, or other corporate benefits.
2) Initiate every single job with a written contract. This contract must define the following:
2a) Your billing rate. Do not include business expenses as additional charges unless travel is required. Your billing rate should be high enough to offset any business expenses.
2b) If travel expenses will exist then you need to write into the contract that you will provide receipts for travel related expenses that occur outside standard billing. There must be language in the contract that defines if there will or will not travel and that expenses related to that travel will be billed to the client outside your standard billing.
2c) Include language that states no work will be performed until an addition to the contract detailing a list of specifically defined requirements is signed by the client. The completion of the requirements is what they are paying for and indicates the work you will be doing. Do not provide any other work and do not perform any other work. If you act as a charity and give away extra services or work outside the requirements then you are not ready to work on your own.
2d) Define the deliverables and any other external requirements. You probably do not read people's minds. If a client wants something specific then they will provide with you with some sort of rough specification.
2e) Include language that you will not provide additional work outside the defined written requirements.
2f) Include language that a contract may be dissolved by either party at any time. Indicate that the earnest money will not be refunded, but all billing will be refunded if the contract is not completed to specification.
2g) Have a lawyer write the language of your contract and you need to review and question that language for clarity. Lawyers often do not speak human language, and sometimes they must be brought back down to Earth. If a client is not capable of understanding your contract then they likely won't follow it and you likely won't enforce it.
3) Charge earnest money. Some clients believe they have the vision of Leonardo and Michelangelo combined, but are completely surprised when work created to the letter of their specifications does not live up their expectations. Under such conditions the client may want you do the work over without charging extra. You are not a charity. Charge a flat entry rate that is two to three times greater than your billing rate up front. This is investment revenue to ensure that at least you get something if the client backs out before you can finish the project, which often occurs if you refuse to give work away for free.
4) If work is performed to the letter of the specifications provided to you and the client is not happy then submit to the client an additional contract and call it a Change Addendum. If they don't like the result then they can pay you more money to perform more work or they can go forward with the work provided. You are not a charity so never perform the same work twice without billing twice unless the work fell outside the written requirements.
5) Do not sell more than your capabilities allow. If you have been writing JavaScript for a month do not expect to sell your services as capable to build an interactive AJAX ready site based entirely off JavaScript interactions. If you charge high enough and attempt to defraud your client they will likely sue you. If additional skills are required then refer the project to somebody else or hire a partner.
6) Never start any work until all requirements are very specifically defined. This may take several meetings and many communications to the client. Keep track of this time, because time spent planning a project is work that should be billed. There may be dependencies that exist in development necessary to determine requirements at a later stage of the project. In that case break the project down into phases and mandate a list of requirements per project phase. Again, do not perform any work until the requirements are defined, written, and signed off.
7) You are not obligated to take every client that asks for your services. You are free to turn anybody away without justification. If a client does not appear to be reliable or you perceive they will waste your time then don't take their work. Time is money and you are not a charity.
8) If a client endlessly wastes your time then simply dissolve the contract, refund any paid billing, and walk away.
9) Charge like a lawyer, and never provide a quote. A project takes as long as it takes to plan and perform the work. That time is entirely relative to the requirements and nothing to do with the client's checkbook. Tell the client your billing rate and if they are dead set on a quote then you can give them an initial estimate of your time and they can figure out a quote on their own. Just remember to tell them that estimate is not reflective of a quote, and even put such language into your contract.
10) Always provide the best quality work and not the fastest work. This is why you get to charge like a professional. If your work takes a bit longer than some other comparable consultant simply explain the value of your service with regards to accessibility law, adjustable features, and efficiency, security and so forth. Through explaining the importance of these features clearly into the defining of the requirements you may be able to alter planning decisions from the client for the benefit of the project's quality.
11) A client is the boss and pays your bills. Even after you try to talk them out of it they will likely make a very bad decision. Do not argue. Simply do your job and move onto the next project. If you cannot heed this advice then you are not ready to work as an independent consultant.