You mean this isn't 10 years ago when you needed every pixel to make a decent size print if you wanted to.
I think that unless one is one needs to offer the hugest prints possible, that it's not worth worrying too much about. But, at this point, a 12mp camera can afford to crop down by about 1/4 and still have to place ones nose on the paper in order to see pixels. And if one has an 18mp camera, one can crop quite a bit and still have a image that's big.
I personally, hate cropping for reasons other than liking a different aspect ratio for the image. But that's mainly because I'm picky and so used to needing the extra pixels that my mind has a certain amount of rigidity on the subject that will take time to break.
I try to use live view when I can. wide angle or tele seem to work the easiest when translating to what I see with my eyes. But middle focal lengths give me the most 'cropped' feeling, versus what my eyes see. So, I end up very confused about how close/far I should be to portray the subject well.
Use a tripod, and make sure to sweep the edges of the viewfinder before you release the shutter.
Also, realize that most optical viewfinders are not 100% so, you're only seeing probably the middle 95% or so of what the sensor is seeing. I think even with the 7D it's not a 100% view it's approximately 100% so there's a slight disagreement between the viewfinder and the sensor.