A large portion of the email I get is from right-handed parents who have some kind of concern about their left-handed child's handwriting. Some of them are in conflict with day care workers or teachers who are trying to force something on the child. Some are worried that their child may be dyslexic. Some just want to know what certain writing techniques mean.
Please stop worrying. In most cases, everything is just fine, whether you know it or not. Lefty or righty, every child is an individual, and every child has his or her own way of learning new skills.
Concerned about mirror-image or backwards writing? See these comments from the U.C. Berkeley Parents Network: http://parents.berkeley.edu/advice/preschoolaged/reversewriting.html.
Concerned about a hooked or twisted writing position? See my illustrated article on this website, by clicking on "Writing Left" in the menu.
The most important thing you can do to help left-handed children is to relax and focus on other aspects of life. Handedness is not a problem unless someone deliberately turns it into one. Keep an eye on what's happening at school (even pre-school) and don't let some egotistical hack who claims to know everything pressure your child into using one hand exclusively or switching from one to the other.