Name 15/04/28(Tue)19:07 No.5355
Atually, it's pretty easy.
If there are two girls but they are looking at you, that means that it's either a threesome/foursome/any kind of orgy with guys or the guy (in Evangelion doujins usually Shinji) fucking one in the first half and then the other in the second half. Even if the cover is symmetrical docking; they look at you? It's very rarely a yuri doujin. They look at you and it's like they invite you, so a guy joins them in your behalf. It might have a few pages of yuri at best, often it doesn't, but sooner than later a guy or more joins.
If the girls are staring at each other it usually is a yuri doujin. No guys there. The girls are hot for each other and don't want any filthy dick in their way. They don't invite you to join, they simply want each other.
Of course, none of this rules apply to anthologies, since you will find everything there. But in average doujins from circles this rule works most of times.