I run a next gen Marvel game (thesupermods) and most of the interest is luck. XD Stuff tends to explode when one person joins who just happens to have a bunch of friends that want to jump in. But! I've found that having a unique premise and a good-looking ad in the right communities helps. Supercity advertises in six: anythingbuthp, marvel_this, marvellous, oldschoolrp, pimp_my_game and x_menrpgads. I put ads in the same communities when my last game started, too (though it died for reasons unrelated to advertising and general interest).
Keeping everything simple and easily accessible in your mod journal helps, too. For me personally, when I look at a new game I need the premise, rules, and FAQ clearly marked and easy to read. Depending on how complicated your AU is, a clear effort toward world-building tends to be an upside. I prefer not to lock down my comms just to make my life easier and so prospective players can read the game and get an idea of whether they'd like it or not, but I understand why people keep their stuff locked, so that's either way.
I think the best way to go is to make everything look good and easy to access, and put effort into what you have in the mod journal. If you don't look like you give a damn about aesthetic or don't seem like you care if stuff is convenient for your players, even the most patient and understanding people will decide to look somewhere else.