Along the same lines as showing/hiding form fields and labels at runtime, it is often useful to change the text of field labels based on other events. This is an easy enough task which isn't really all that different than showing or hiding the label.
You just get a reference to the td cell containing the label, which we talked about before is named the same as the schema name ending in an '_c' suffix, and set the inner text for the cell. Here's a sample for a field with the schema name “new_myfield”.
crmForm.all.new_myfield_c.innerText = 'My New Label';
Make's it easy to change labels if needed to match things that are happening on the form. This could also be used to hide labels altogether as well.