contracting rates are a little confusing for starting self-employed contractors. you want to attract work and typically undersell your skills, as you may think you're not as efficient as established contractors.
you have to keep things in perspective though, and balance the above and other considerations. Contracting rates have to cover holidays, sick, travel, and other expenses, which businesses cover for (non-contract) full time employees. Therefore contracting rates should be higher to compensate. In regards to setting a low rate to attract work...it's difficult to later raise rates with existing customers, which (the rates) may be inadequate. In my opinion you should set the rate reasonably in line with current market going rates. If you think you took longer than reasonable on a project because you're just starting out, then just don't bill all the hours initially.
if you provide quality work (to an agreed standard) then customers will pay well. Just don't leave yourself open to free lifetime upgrades/bug-fixes.
good luck.....if you get stuck in code, perlmonks can help