Half hitches are temporary knots which are not intended to support a lot of strain or pressure. They are employed to make other knots strong by creating a safety (restraint). The half hitch is one of the most widely used knots and is applicable in all kinds of situations.
Step one - Pass the end through from below or around an object. I'll explain tying half hitches as if you were going to tie a safety on a bowline.
Step two - Pass the end behind the standing part and into the eye of the loop that has just been created. The first half hitch is complete.
Step three - Continue the same operation two to three more times. Tighten your half-hitches one at a time. See the figures below.
It is not necessary to know many knots. If you understand these three, they will provide you with a good foundation for any of your investigative needs. The most important thing is to know how to tie them quickly and properly and the only way to gain the needed confidence to do this is to practice the knots over and over again until the movements become completely automatic and instinctive.