If you're searching for a specific page of notes, use the Page List task pane, where your pages are listed by title, showing the section name and the date of each page.
On the View menu, click Pages Sorted By Date:
The section, the page title, and date are listed.
You can sort the list by section, title, or date.
Sort the list in ascending or descending alphabetical order.
Choose what areas to include in the list: this section, this section group, this notebook, or all notebooks.
You can see a Help topic for some more search tips.
If, for example, you know roughly when you took some notes, but just browsing hasn't revealed them, try searching by date. If you can remember what you titled a page, sort the page list by title. Or if you know a page is in a particular folder but you can't remember which section, just search by section.
Note If you use a Tablet PC, OneNote will automatically search over your handwritten notes even if you haven't converted them to text.
Tip There are some tips available for successful searching. Just click the Search tips link at the bottom of the Page List task pane.