Practice, practice, practice. If you record practice sessions of your podcast, you can write down three or more aspects of your voice that you want to improve, and then aim to resolve those issues.
Similarly, listen to your old podcast episodes for moments when your voice is weaker than you'd like it to be. Then, make sure you don't make those same mistakes in the future.
Finally, slow down. The most important thing is that your voice is loud and clear, so that you listeners can connect with your message.