That's a huge subject.
There are lots of vids on Youtube. But honestly your best bet is to buy a decent book on the subject and take a lot of time learning it. There are many to chose from, including some in the Dummies series. They at least will start from first principles. There is no short cut.
Your question has inspired me to try to relearn all the stuff I've forgotten or corrupted in my mind from misuse - more books to come!