Expalin to me how would you troubleshoot in packet tracer?? What commands would you use?

For example you have 3 netowrks 1, 2 ,3 with 2 pcs in each network. How would you touble shoot if you could not ping pc1 to pc2 in network 1. Can you give me steps??

Also if you could not ping from network1 pc1 to network 2 pc1 ??

And if you could ping from network 1 to netowrk 3 but not pc 1 on netowrk 3??