When you're first entering a new keyword, go into Library mode, select All Photographs from the Library panel, drag your Thumbnails slider all the way to the left so you can visually identify as many of your images at once as possible, and then use the scroll wheel on your mouse to quickly move through one page of images at a time. Press Cmnd/Ctrl and click on the top border of each of the thumbs that suits the particular category you're looking for. Go to the Keywording panel. It will be showing all of the keywords used for any of the selected images. Those that apply to all of them won't have an asterisk. If any of the keywords you want to add to all of the images has an asterisk, simply delete the asterisk. Now add any of the other keywords that you want to pertain to this entire collection.

There is a slight variation to the above procedure that a lot of people like. Just use the Paint tool to add the keywords to each image you click. To use the Paint Tool, click the Spray Paint Can icon in the Library's Toolbar. A keywords field will show up next to it. Enter the keywords you want to add to a given category and then just go through the thumbs and click on the images you want to add that set of keywords to.

Whenever you forget to add a keyword to a group, Find the group, then just add the keyword you forgot.

Whenever you want to go back to the whole "All Photographs" collection for the Catalog you want to add keywords to, be sure to delete any keywords that are currently in the Find field. Then you can repeat the above steps for any of the other categories you want to keyword. I do this from time to time to double-check for each type of photo; or for each category I may find a new and useful keyword for.

Lightroom will automatically complete the typing of any word you've entered into the keyword list. If it's not the right word, just keep typing until you type the letter that's unique to that position in the word. If you type a brand-new word, it is automatically added to the list.

One thing Lightroom doesn't do is automatically attach the parent of hierarchical keywords. Now there's a great suggestion for Adobe's future releases. So if you have Animals as a subject header, than anything you label with cats, dogs, parrots, or snakes would also be labeled with Animals.

Get keyword lists from some stock agencies and professional "camera clubs" such as ASMP (American Society of Media Photographers). Make a word processor list of all the categories you can think of as you flip through your libraries. This will become your consistent list. Then organize them into parental categories. Then just cut and paste them into the Keyword Tags field in the Keywording panel. When you've figured out the keywords that work best for a given category of photography, put them all into one of these field and then open the Keyword Set menu and choose the ones you need for the particular image to which you're attaching them.

If you have more great and time-saving suggestions on keywording, please don't hesitate to comment below.