While Google Reader's new search feature has many limitations and is still far from Bloglines, there are some features that help you find a post faster.
1. You have three ways to view search results:
* snippet view, similar to the way Google displays web search results. This view helps you decide if a result is useful by showing snippets related to your query.
* expanded view, that shows the full posts. Choose this view if you want to read most search results.
* list view, which only shows the title of the post. This is useful if you want to explore a lot of search results.
2. Exact matches: put quotation marks around your search terms to get the results that include an exact phrase.
3. Wildcard: use an asterisk to replace some words in your query. This only works for exact matches. Include an asterisk for each word you want to replace.
For example: "has * * * new features" matches: "has just announced several new features", "has recently added two new features", "has released a few new features".
4. Negative searches: if you want all the posts that contain [book search] but don't include [Google], search for [book search -Google].
5. You can bookmark searches. Google Reader doesn't offer an option to save searches, but if you find yourself repeating the same searches, bookmark them. The latest Google Reader update added transparent URLs so you can use the Back button or bookmark pages.
6. Search using the keyboard:
/ - add focus to the search box
Tab - choose a folder or a feed to restrict your search
Enter - instead of clicking the Search button, press Enter
Alternate between the three views: 1 (expanded view), 2 (list view), 3 (snippet view).
To select the first search result, press j. Then you can go to the next result (j) or the previous result (k).
Press Enter to read the full post and go back to the search results by pressing Enter again.
7. View a search result in its original context: make sure that the result is active and press v or middle-click on the title. This will open a new tab/window with the blog post or news article.
8. You can search other people's shared items and public folders. Assuming you know the numeric ID of a user, do a search in your shared items and replace your ID with another ID:
Example: here's a search for [Microsoft] in Robert Scoble's shared items.
9. Because Google Reader is not yet able to rank results by relevancy, a good way to make sure you'll find a post in six months is to star it. When you want to retrieve an important post, restrict the search results to the starred items first.