Metro is spot on with what he says above.
If you have mates you train with join the club they are in, and if your male and under 30 then you can't join Vets as they are Womens (vet and non-vet) and Mens veteran club only.
If you have junior offspring wanting to race, either KOCC or HD would be the club as you and your children can be in the same club, KOCC has more junior racing they run a junior race most Saturdays if enough numbers turn up, HD runs junior races at the crit once a month.
Juniors from both clubs are more than welcome and encouraged to race at both clubs races.
I have 3 relations all racing in KOCC ranging from 12 to 66