I've had Lightroom for a few years now and never really "got" it. However I decided I was really going to sit down with it and give it a go with an Adobe Photographer CC trial.
Once I got the idea of collections, it's started to "click" for me.
My workflow (for now, until I learn more)
1. Insert card and import photos from each shoot into LR. If there's more than one shoot on a card (i.e. I took pictures of the forest, then I did some portraits a little later), I only import each "session" into a collection that I name appropriately (i.e. "Walk in the woods 11.15")
2. Then I go through and pick and rate my photos in library mode. The picks I pick with the "P" key and then give a 0-5 star rating (press 0-5 while on the image). Photos that are blurry, I don't like, or for whatever reason just want to reject I press "X" on and reject them.
3. Once I'm done, I go up to the Photo menu and select "Delete Rejected Photos" and I remove them from disk. Storage is cheap, but I've probably got every NEF I ever took with my D40 and what good is it doing me? It just makes it more cumbersome to go through my images.
4. I then go back through the images I kept and ensure I like the 0-5 star ratings I gave them. Then switch to "Develop" mode at the top right.
5. I'll then apply the appropriate lens profile to the images. I need to figure out if I can automate this, but I don't know how at the moment.
6. I'll then start playing with white balance, sliders, sharpening, and lens profiles. All of this stuff works best if you shoot RAW - for example, some lens corrections only work on RAW files. To be totally honest, I really have no idea what I'm doing when it comes to sliders. I guess this is where the subjective part of the art comes into play. I'm sure there's a technically "right" thing to do, but I just wing it to get the look I want.
- Press "J" on the keyboard - this will show you clipping as the camera does - basically, have you used too much of any one slider to clip out detail.
- I'll change the white balance to match the type of lighting I was shooting with. If I don't like it, I go back to "As Shot."
- I then click "Auto Tone" - If I like it, I'll stick with it. If not, I'll play with the exposure, whites, blacks, highlights, and shadows sliders until I get a look I like. Sometimes I'll zero everything out and start over. It all just depends. I'll generally go -100 to +100 and just stop the mouse where I think it looks good.
What I look for with these sliders is to look at extremely bright and dark parts of the images. For example, if you're editing a photo of a woman and she has a white dress on, I might bring the highlights down because the image as displayed has basically lost detail in the folds or small details of her dress. Same with blacks - you might lose detail in extremely dark areas that you can recover with the sliders.
- I then play with the Clarity, Vibrance, and Saturation sliders. Be careful with these - these can add a heavily "processed", almost ethereal look to your images if overdone. Sometimes that's what I'm going for, but sometimes not.
- I always look at an image in black and white. Especially if you were pushing the ISO and get some grain you didn't expect, I like the grain + B&W look - but that's just me. Again, there's probably a "technically" right way to play with these sliders, but I just go with what looks good to me.
- I then go down the side and look for the sharpening slider and give it a little sharpening if it looks good. Too much sharpening will make an image look strange. Again, subjective here.
Repeat for each image you want to process.
At this point, I'm generally done. If there's an image where I need to remove some lint off of a shirt, remove a pimple or an unruly eyebrow, this is where I tell lightroom to "Edit a copy in Photoshop with Lightroom Edits." In PS, the clone stamp tool does wonders. I hear the healing brush does wonders as well, as well as some careful selection and softening / gaussion blur (if you have a subject that has some heavy acne or rough skin.)
I then export the photos from Lightroom to whatever format I want. I have export presets for The Web, Prints, and of course a preset for Nikonians (Limits long side to 1000 Pix!)
I'm sure there's a million other ways to use these tools, but this is the workflow that seems to be working for me.
Oh, backups are important! I use Backblaze - $5/month unlimited continuous cloud backup. As soon as stuff is imported, it's backed up within the hour.