I rate all images from 0 stars to 5 stars using Photo Mechanic. 0 stars means it's not a good enough image to ever use for any reason. 5-stars, as you might guess, are my best work. That also means I can go ahead and delete 0-star images and save the disk space. To rate images, I double-click the first image and unclick the Zoom box in the right panel so I can see the entire image in the window.
The easiest way to set the stars for me is by holding down the Control button and clicking 1 through 5 for a 1-star through a 5-star image. If it's easier for you, there's a "star box" in the lower left corner of the image where you can click on the number of stars you want. For 0-star images, you can either leave them alone if you want to take one final look after rating all the images, or you can just go ahead and click the Delete key if you're sure about them.
I generally take a second pass to make sure I've rated them properly. To do this, I close the Preview window that has been showing me the images large, so that I'm back to the main window showing just thumbnails of all images in the shoot. Look at the bottom bar of the main window. Near the bottom right corner, there's a box of stars. Click on the 1-star and it will turn grey... and all the 1-star images will be hidden from the window. This lets you selectively look at only certain star ratings. So you can look at all the 3-stars at once, all the 4-stars at once, etc. This helps me determine if I've rated everything evenly. It also helps me see if I've been too easy or too tough on this shoot. I then adjust the ratings accordingly. FWIW, I generally don't rate "on the curve." In other words, there are quite a number of shoots with no 5-stars, because if I'm saving that rating for my best work, I want people to be able to count on that.
Once you're done adjusting the ratings, move the images on to the "-4 Set Classes" folder using the same Command-Y method noted earlier. And as noted earlier, you can delete the "-3 Rate" folder once it's empty if you like.
The next step is to set image classes.
Note: I've recently experimented with rating and setting classes (step 9) at the same time. It works quite well. Give this a try and see if it works for you.