This is a really hard thing for a lot of photographers, maybe even me. The simplest way to cull photos is actually not take them in the first place. However with digital cameras it is just too easy to keep pressing the shutter button, well until your memory card fills. These cards are very affordable (now less in most cases than a roll of 35mm film). So the temptation is there to "Spray & Pray".
I don't think there is a perfect way to sort and organise photos. It is a very personal thing in reality. However I don’t really like being forced into a specific "workflow" that must be religiously followed (are you listening lightroom?). Trying to rate images immediately by "chimping" (looking at the LCD screen on the back of the camera), not only wastes time you could be taking photographs, the ambient light will probably make the image hard to view and evaluate properly. I know in my bones that as you first load and review your photos (whether that is from your phone onto a web service or from a DSLR onto your computer), that the right time to do the culling is as you first view your images. Trust your first impressions and gut feel they are probably right.
Here is my list of what should be discarded immediately
- Very poorly exposed (see caveat below)
- Subject out of focus (the degree of sharpness is a personal thing because post processing sharpening has come along way)
- Subject is awkwardly cut off
- The photo is not flattering or shows potential for embarrassment (no definitely don't post it on instagram delete it now!)
- There is a set of very close photos/images (unless that are really good just keep one, it may be the first rather than the last!)
To be honest you can "rescue" a lot of poorly exposed photos, particularly if you have the RAW original, but if the image doesn't "grab you" to begin with, you will just end up with a boring yet better exposed image. You may as well discard it.
At the same time you are culling you should also flag those images that have potential for post processing. I have found I much prefer doing this stage in Picasa or Corel Aftershot Pro. In Picasa I delete both the jpeg & RAW files immediately and flag the photos with potential with a star (Picasa only has a one star rating). In AfterShot Pro I don't bother importing the images into its library/catalogue but I do use their flags, which are the same as lightroom's also I'm finding after shot's compare view (like lightroom's survey mode) nice to use (picasa can compare two images nicely but after that its complex) and also after shot's little magnifier is a real gem. The nice thing with after shot is you can save the metadata and ratings done at this stage to an XMP sidecar file and these settings will be loaded in lightroom later. The big advantage of this approach is speed (if you have a full 4GB card) I can pretty much guarantee you will be able to the load the photos from the card, do the culling and rating in Picasa and/or AfterShot Pro before lightroom has even finished importing the photos off the card.