A couple of things you can do.
First, you can up the LCD's sharpness to the max (7, I think?) and change any other in-camera settings that will help the image look "right" so that the displayed images take on more of the character of the finished article: doing so is harmless to the image because the in-camera settings can't be read by any other RAW converter than DPP, and can be turned off in DPP. I've done this with my 40D for - well, years now, and honestly I've had zero problems in deciding which are sharp images and which are not.
In fact I'll go as far as to say that my 7D's LCD - nice as it is - adds nothing to the "user experience" for me, because now everything looks good on the LCD, which is no more representative of reality than the 40D's LCD in terms of deciding on which files are keepers.
Which brings me to tip number 2: don't chimp. The fact is that the camera's LCD is the worst place to make decisions about whether a given image is worth keeping. There's no strong argument for doing this on the camera - if you're running out of room on the CF card, just put another one in.
Do your culling at home on your computer, on a big, properly set-up monitor, not a pokey little LCD in too much, or not enough, light...
