Adding keywords to your photos in Lightroom is probably not the most fun part of your photo editing workflow. I guess you would rather spend time on your creative process with making your photos come alive or be out taking more photos.
However, managing your Lightroom keywords is very useful, because many publishing plugins to Lightroom can recognize the attached keywords and use these in your online portfolio (like on Photoshelter), or on a photography portal like on 500px.com. Entering keywords in Lightroom will save you the time of entering the keywords online. Maintaining a good keyword structure in Lightroom can highly benefit your search engine optimization effort online along with improving Lightroom’s ability to find your photos when you search for them.
Keywording in Lightroom is quite flexible, and you can add keywords in several ways.
Besides, from just adding your keywords in the Keywording Panel, you could instead build a hierarchy of keywords. It takes more time in the beginning, but it pays off later when entering keywords for other images.