Getting started with reverse engineering?

Say have a binary file without the source code available, how to get started understanding how it works?

I found some sources:

• http://decompilation.wiki/
• https://mahaloz.re/dec-progress-2024
• https://github.com/NationalSecurityAgency/ghidra

Can I spot places in the code that make network connection attempts, de obfuscate spyware?