How can I make Betrayal at House on the Hill less confusing?
I'm assuming that your biggest problem is the haunt rules, if you've already played the games several times. 

The easiest way to make the haunts (and their special rules) simpler is to discuss the special haunt rules with other people - preferably people who know the rules well. The Heroes, of course, get to hash out the special rules with each other and come to some sort of consensus, but the Traitor is alone and needs to muddle through things himself.

There are three things that can help here:


If there's somebody not playing the game, have the Traitor talk it over with them. Even if they're not much of a gamer, simply discussing the rules can make things clearer. If there's nobody handy, then explain the rules to a rubber duck.
Go get the updated Hero and Traitor books from Wizards.  While you're there, get the errata for the regular rules.
Just relax and have fun. If there's serious confusion in the rules, make a quick ruling and work it out after the game.

If you're really worried, then have the whole group hash out the rules and/or check the errata, even if you reveal a few small things about the Heroes or Traitor while you're at it.



If your problems are with the regular game, then make two cheat-sheets: one for the regular rules, and one for the standard haunt rules (movement past enemies, combat, how the traitor &amp; monsters ignore all bad effects, etc.).