How do you know when you have established alpha with your dog?

She listens to me, follows me around the house all of the time pretty much. Have taught her all basic and some pretty cool tricks, and she listens thoroughly. She wont listen to anyone like she listens to me, I dont ever use violence ever!!!! I watch cesar millan a lot, and tried looking this question up on the internet could not find specific results. She has never growled at me and when i am around she does listen to everyone else. Just wondering if anyone knows if that sounds like i have established myself as alpha or not, she is german shepherd/lab mix and unknown other breed. Thankyou if anyone can help. Also, I get the most respect out of her than the rest of the household to the point sometimes when i come back home i get some complaints, but like i said when i am home she will behave.