I like to Keep Things Simple.
Many designers offer services by providing a quote for a specific job.
The problem I have with this is that it encourages mediocre work. Any job that is completed quickly earns the designer more pay per hour, and too many people rush to find the easiest solutions to get the work done faster.
When a job is done correctly, the solution is eloquent. Code always works, websites always load quickly and work across all browsers, and later editing is simple because the work was done right the first time.
To keep things simple, I use a nice, fair flat rate. $35.00 per hour. One fee for tutoring, web help, photo editing, etc. This keeps everything I do fair and simple to keep track of . I am upfront about everything I am doing and exactly what you’re paying for so there are no unpleasant surprises.