I'll try and post more later but for now...I usually play on 3 sites, drfqualify, horsetourneys and horseplayers. horseplayers is run by horsetourneys and took the place of nhcqualify and bcqualify which were run by drf.
Horseplayers only has NHC and BCBC.
Horsetourneys has some NHC but mainly has all the fantastic brick and mortar events-the Del Mar and Toga plus others.
drf has non-NHC and BCBC such as Del Mar, Toga, Keeneland and their own World Series (play in their free tourneys every Wednesday and most? Thursdays).
Basically, there are low level feeders, qualifiers and main tourneys. Usually, not always, it is feeder>qualifier>Main Tourney and if you win main tourney you have entry to Del Mar's next week 8000 tourney for instance.
