Is there a general method for working out electron configurations?
There is a semi-empirical method to fill the atomic orbitals: atomic orbitals are filled  in the order of increasing n+l. If the sum n+l is equal for two atomic orbitals, they are filled in order of increasing n.
This gives the following order for filling the orbitals:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s, 5g, 6f, 7d, 8p, and 9s