Fast way to get new boot SD-Card

Hello Gays,

I have a Default boot SD-Card generated out of the zip file from the net. I will delete all (most) not used Software parts to optimise the start up/shut down time and ROM place (used for my own application).

What is the fastest (easiest) way to delete the unnecessary drivers and functions of the Linux (Kernal)?
Exist the Option to delete function calls in the start Scrips and to delete the Folders for These functions?

Best regards
Edgar