The word "configuration" means "the arrangement of the parts of something." An electron configuration describes "the arrangement of electrons in space around a nucleus."
Probably the least reliable method is to memorize the following list (even though it shows the order of filling of all the orbitals necessary for describing the ground state electron configurations of all of the known elements).
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p
Each "s" gets a "2" electrons.
Each "d" gets a "10."
Each "f" gets a "14."
For example, let's say you have an atom of lithium. Lithium's atomic number is 3. So a neutral atom of lithium has 3 protons and 3 electrons. We would need space for 3 electrons. Write: