Great question! Left handed kids often, and really should, use different techniques to write then right handed peers. For one, the paper should be tilted more the right to make writing easier and more comfortable.
To compensate for their hands covering up several of the words or letters that they're writing, lefties often hold the pen or pencil differently. It's important for parents or teachers to show them the correct way of holding a writing utensil, and to enforce that method.
Another good way to make handwriting easier for lefties is to stick with pencils, and if pens are needed, make sure they are "quick drying" so the ink doesn't smear as much.
Below, I'm including an article with tips for left-handed kids on everything from sports to writing. Hope it helps!