Step-by-step explanation:
Involves hormones: the pill, a pill that you take once daily that stops sperm from joining an egg. IUD, a little piece of plastic inserted into the uterus. Birthcontrol shot, injection of a hormone that stops sperm from meeting the egg.
Forms a barrier: female and male condoms, create a physical barrier between genitals but still allows for pleasure to be felt.
Involves use of spermicide: kind of like a lube that kills sperm. Can be found in creams, lubes, gels, and suppositories.
Protects against STIs: female and male condoms.
The most effective method: out of these I'd say the most effective is the pill, IUD, or abstinence.