What are some top tips for troubleshooting networking issues?

I am quite deep in my IT career and I am embarrassed to admit I constantly struggle with troubleshooting networking issues between servers / docker containers / kubernetes pods etc

For example I am currently running Ubuntu for Windows, running a Kubernetes cluster using Minikube with a docker driver (so the one Kubernetes node is in a docker container) and have Jenkins deployed.

I have portforward jenkins 8080 to localhost:8080 but I get 'Unable to connect when going there in the browser.

The only command I can think of is 'telnet localhost 8080' which returns 'connection closed by foreign host.

What is your general workflow when troubleshooting these kinds of issues?
What are some tools you use to help you with this?
I am a really visual learner, what is a suitable way for me to improve at this?