Expect lots of questions (the same ones, repeated over and over - I think Karern Salloum (the VO) was hoping we'd crack) about why you want to marry a foreigner. She asked me (the Canadian wife) over and over, "How do you know your husband won't run away as soon as he gets to Canada?" At our interview, she was bad-tempered and angry and asked questions in a belligerent way. During the interview with my husband she also threw our documents on the floor. At the end of her interview with me, she angrily asked/shouted: "Can this really be a marriage? Really?" and stormed out of the room, slamming the door. She then called my husband back in and aggressively said: "Your wife just told me she can't have children." (Which I did not say, by the way.)
Good luck.
Several people have told me that if you're applying through the Accra office, you're probably going to be rejected, but will then get in on appeal. Make sure your application has tons of proof you're in a genuine relationship.