Graduation Cap / Bobby Pin help?

I have some Bobby Pins to refrain my graduation cap from falling. I bought them because everyone recommended them and I wanted to avoid embarrassment. I rarely, if ever use Bobby Pins, so I have little to no experience with them. How exactly do I securely clip them on my hair / graduation cap ? What about this x pattern using two Bobby Pins I've seen being brought up sometimes ? I've tried putting them on myself, starting with one on each side of my head and, honestly, I did not do well.