As long as the girl knows how to ease it in... no preparations necessary. Few things hurt as much as when it's forced in.  Had that happen a few times.  It's recoverable but takes time.  Generally the big girls appreciate my ability to take them without any drama and enjoy going to town on me without worry.  They run into guys more often than not who's eyes are bigger than their assholes so to speak.  
   
 One tip I've learned it that the lube needs to go in deep.  At least an inch or two. I recommend Ass Relax.  It has a touch of Lidocaine.