How to make a multiplexer?

Could you please elaborate on the steps required to construct a multiplexer? Are there any specific components or tools needed? Is there a particular design or circuit layout that's commonly used? Additionally, could you discuss the importance of selecting the right input and output signals for the multiplexer, and how they impact its functionality? I'm interested in understanding the entire process from start to finish, including any tips or best practices you might have for ensuring a successful build.