What are the most common early‑stage mistakes when sculpting with polymer clay, and how can I avoid them?

I’ve been working with polymer clay for a few months, but I keep finding myself making the same errors. I want to stop wasting time and material. Specifically, I’d like to know:

1. How can I prevent overworking the clay so the surface remains smooth without losing detail?
2. What are the best practices for building a supportive armature, and how do I integrate it without compromising the final shape?
3. When is it acceptable to undercut, and how do I avoid compromising structural integrity?
4. What drying or baking mistakes should I watch out for that cause cracking or warping?
5. Are there any subtle habits that seasoned sculptors avoid—like the way they hold the clay or the order in which they add layers—that I should adopt?

I’m looking for concrete, step‑by‑step guidance rather than vague suggestions. If you have tried a particular technique that saved you from a common pitfall, I’d appreciate a detailed explanation. Also, if there’s a resource—book, video, forum thread—that you find indispensable, let me know.

Thanks in advance for any insights.