Lisa, easiest way except when your kids don't care if they're late - or miss altogether.
difficult child gets herself up. Amazing, I know. D was a different story. It was like trying to wake the dead. He'd curl up in a ball, whine, yell...he'd do it all. So, I would just stand in his room and in a really annoying monotone voice say his name over and over and over and over and over, without stopping until he got annoyed enough that he got up. Sitting up didn't count. He had to be physically out of the bed.
Toward the end of his school years even that didn't work. I was so glad when he was out of school. He's not this way about getting up for work.