'nearby' means ordering your query using the <-> operator.
'meeting criteria' goes in the where clause.
For example to find interesting things nearby in postgres:
SELECT * from interesting_things as it where (it.A ='A' AND it.B ='B' AND it.C = 'C')
order by it.location <-> point '(current_lat,current_lon)' LIMIT 10
http://wiki.postgresql.org/wiki/Whats_new_in_PostgreSQL_9.1#...