nuB questions: how to stop two instances of three? also, who should ow

hello:

first is a peace of mind thing: who should own the /usr/local/bin/ postgres stuff? root or postgres?

more inportantly, i've got three "postgres" processes; does this mean i've got three instances going?

i created a default database...
[gus:~] postgres% /usr/local/bin/initdb -D /usr/local/pgsql/data
... then decided i wanted my data in a different directory...
[gus:~] postgres% /usr/local/bin/initdb -D /Users/postgres/Documents/pgdata
... and may have run the first one twice <g>.

i only want the last one; pg_dump seems to dump the data; dropdb needs a name, and i'm not sure if this is the right command anyway.

help?