The best way to remember the spelling of beautiful is to remember the following :
You have to be a beautiful person both inside and out. So beautiful begins with 'be a'.
Another funny way is to learn how Jim Carrey spell it out in the movie 'Bruce Almighty' when his car gets stolen. It goes like :
"B..E..A..UTIFUL!!"
Here is the video link:
https://www.youtube.com/watch?v=UPphDSc6ZEE