Those are the advises that worked for me:

Real-world use-cases

Experiment and learn Kubernetes basics with real-world usage. Try to run your self-hosted services in it for instance. Something basics requiring storage and an external URL are enough. It will give you an overview of the Kubernetes documentation and you'll need to learn about services, ingress and volumes (PV, PVC).

Learn by doing first. Then dig more deeply into the theory and more complex use-cases.

Prepare the exam with the Udemy course

The easiest way is to take the CKA preparation course (around 11 euros), it is super complete and you have practice labs, and exam preparation questions (the number 2 and 3 are enough.) If you understand every step, the exam would be easy

Additional tricks

Use the shortcuts

• -n namespace-name instead of --namespace namespace-name
• use -A instead of all-namespaces, for instance: kubectl get pods -A
• To get all resources and have a namespace overview, you can write kubectl get all
• alias k=kubectl. The only bash alias I used, and it is enough.
• !$ allows you to use the last argument of the previous bash command.
• cat > my file let you write super quickly in a file. Then modify it with vi.
• Learn your editor (vi, nano), be confident in a terminal.
• Learn all the Kubernetes shortcuts such svc for services.

Notes

• If you prepared with real use-cases & Udemy course, you will have enough time to verify every exercises.
• For "complicated" question such set-up a cluster with kubeadm, take your time. I missed the 100/100 because of this one. I went too fast and fucked-up the boxes :D