To calculate errors for fit parameters using the least squares method, one approach is to vary individual parameters while optimizing others and track the increase in the sum of squares. This method helps in estimating the sensitivity of the fit to changes in parameters. Alternatively, utilizing existing fitting programs can simplify the process, as they typically include built-in functions for error estimation. These programs can provide more accurate and efficient calculations compared to manual methods. Understanding both approaches can enhance the analysis of fit parameters and their associated errors.