If your requirements are less than or equal to market rate salary, ask for market rate salary.
However, if your salary requirement is greater than the market salary (no matter how much more), I would first come in with the market salary (or slightly below). The goal is to get an interview, meet the hiring manager, and figure out exactly what the job requirements and duties are. When you are sitting down with the hiring manager, come out with your original salary requirement.
When someone contacts you asking for your salary requirement, it's usually HR trying to filter out candidates which are too expensive for the company. The problem with this approach is that they risk filtering out really good candidates. They have no way of knowing this from pieces of paper (your resume, CV, or cover letter). If you score an interview, then the hiring manager (not an HR specialist) has a personal impression of the value your skills bring to the company. You also have a better idea of what exactly you'll be doing and how much you think those duties cost.
Lowballing HR is not a waste of time. If you are the right candidate, hiring managers have the ability to offer a salary beyond the 'stated' salary range they give to HR for the job posting. However, if you never get a chance to make a personal impression, you are simply another line item in their list of candidates.
