I have just found this neat trick/acronym for helping to select the correct verb "to be".
Ser: Acronym = BOOT.
B....Basic characteristics.
O....Origin.
O....Occupations.
T....Time.
Estar: Acronym = FLAT.
F.....Feelings.
L.....Location.
A.....and.
T.....Temporary characteristics.
I hope you find it helpful.
Ser or Estar
sjlkh
March 10, 2011