In Lightroom 4, how do I apply the same title and keywords to multiple photos?
Alternatively, how do I apply title and keywords of a photo to another set of multiple photos?
The easiest way it to use multiple selection. On Windows that means using CTRL-Click to select more than one image or SHIFT-Click to select consecutive images. Then, you just type in the keywords in the appropriate box on the right panel and press enter.
You can select images by filtering first. If the filer-bar is not visible, press / and then select the criteria you want. Once only images you wish to apply keywords to are shown, press CTRL-A which selects everything. Again type keywords in the keyword box and press enter.
Note that you can also apply the same keywords to all images as they are imported by putting keywords in the keyword box in the Import dialog.