one way is to put it into your forum sig 
Saber Spectre Inv / EM Tanker on Guardian
Wraith Scimitar EM/ EA Brute on Guardian
Attack of the s00p3rphr34k ID 49744
there is even a thread telling you how to promote your arc
http://boards.cityofheroes.com/showflat....=0#Post13277897
I stand on top of City Hall and shout, "PLAY MY ARC," at the top of my lungs.
Doesn't get me any plays, but it does wonders to reduce stress!
That blue thing running around saying "Cookies are sometimes food" is Praetorian Cookie Monster!
Shoot on sight, please.
Here's a whole board mostly dedicated to such.
Heh, I just noticed that they didn't really create a new board, they just used the old "pre-merge" Villains board. 
Dec out.
Is there an established way to plug our MA arcs on the forums?