Do you have any tips for part-time PhD students?
If you're doing a PhD part-time, the tips I'd give depend very much on what you're doing with the other part of your time.
If you have a part-time job with predictable hours, it's easier to manage the two demands than if you're running your own business, which is easier than if you're doing a PhD and have a full-time job and you're raising kids all at the same time.
But I'll try to give a general answer anyway.
First, treat the PhD with a level of priority that can compete with the other demands on your time. This means that sometimes you have to say no (or not now) to important things so you can work on your PhD.
Set aside time for your PhD and protect that time. If you can't or won't do this, it will always be pushed aside by other demands.
Second, make sure you don't get isolated. Connections with other students and academics can make a huge difference and you might have to make extra effort to make these happen.