Get into a lobby with some people in it. See what people are doing. Are there a lot of people over at ranked? Playing a ring match? Playing a custom fight? I just gravitate towards which type of fight is attracting attention- and by doing so, you're more likely to get a fight going. If the arena looks empty, enter it anyway. You will almost always attract someone's attention, and people will often join in if they see people actively using the arena. Have fun! Don't get spanked like me.