Painless Guide on DLL Debugging

I have seen many people that can not understand how debugging a DLL is done, and I've recieved a couple of requests on such topics, so I'm writing this guide in the hope that someone can find it useful.

This guide is not for 100% newbies, those who don't know/didn't use a (disassembler, debugger) before should read more on that topic before reading this guide.

In this guide I don't include too much of "proof-of-concept" examples, it's a general idea that I want to deliver, that's all.