Like Photoshop, Lightroom is a powerful piece of software. Sadly most of us learn the basics and don't take advantage of all that is has to offer. One powerful feature is called the "Survey View." Are you taking advantage of it? If not, take a couple minutes to watch this two minute video where I go over how to use the tool and the shortcut to get there.
The survey view is an especially useful tool when you have a few images that look very similar but you can't quite decide between them. By bringing them up in this view you can compare the images side by side and see which one looks the best. I have found that it works best when you have 2-6 photos that you are trying to compare.
Before using the survey view I'll first close my menus in Lightroom by hitting Shift-Tab. By doing this I am making for screen space for the images to fill. While in the Library Module (shortcut: G) I'll select a few images and go to the survey view by using the shortcut "N" on my keyboard. While in this view I can now flag, rate, or label the image that I like the best or reject those that I don't want to use any longer. To go back to the Library Module just hit the letter G again. Or if you highlight an image you want to edit you can hit the letter D to be taken to the Develop Module to do your edits.
Now one other way this can be done in Lightroom is using the compare view (shortcut: C) however I have found that I like the survey view more as I can look at more than just two images at a time. Hope you found this quick tip useful and are able to implement using the survey view into your workflow to speed up and be more accurate about choosing the best images for your clients.