Ragnarok.Hevans said: »
well the flash references the main character doing work for the guy from arrow and one of the chicks makes an appearance. so i think arrow takes place prior, but i dunno where daredevil fits in. let me know if you like it. i've been trying to find new stuff to watch.
Barry appears in season 2 for a couple episode (?)
so the Flash (S1) series actually kicks in on Arrow's Season 3.
while each show is a stand alone, characters from both shows do make a random appearance between each other, and they do mention the other group's current events randomly.
Arrow Season 4 and Flash Season 2 kind of spins off into "dc heroes of tomorrow" season 1
there is one episode (Season 2) that crosses over to Super Girl's episode, as Flash makes appearance there, but people who are oblivious of this wont even notice it.