i think first you need to shortlist the few schs you want then call them up n check if there r any vacancies.
some popular schs might need to be place on waiting list..
but i see your boy still very young, only 5 mths old worr.
but then again, no harm searching now, n enquire, since some schs have waiting list up to 1-2 yrs.
usally for CC you can register anytime, they will just place them in the class according to their age.