Tonight it's Claudio Vargas against Wandy Rodriguez. This is as good a time as any to point you to baseball-reference's game previews, which are an amazing (as always) source of well-organized (as always) information.
For instance, you can find that Rodriguez has had a game score of 50 in each of his last two outings, Vargas has won his last two outings against the 'Stros, Milwaukee leads the season series 5-2, and that Corey Hart has a 1.310 OPS against Wandy. And, of course, a few other tidbits. I opted for the more encouraging ones.