Practice! Practice! Practice! But first ask two questions. What do you like about your signature? and What do you dislike about your signature? Decide which shapes look good and what shapes look bad. Some cursive letters look better and some print letters look better. I found that the letter "G" looks better in print than cursive. Add elements to your signature like shapes, squiggles, etc. Do your research.
One last thing, be prepared for questions and sometimes aggravations. Banks will pause when they see that your signature is different, they may give you a hard time when cashing a check with your new signature, credit card companies may do the same and let's not forget the IRS and the dreaded tax returns. If you change your signature for the better than just be aware there could be some growing pains.