Find the most recent annual information available on global warming

an optimal query: global warming 2005..2007

Recent annual information may be replaced by a search for a recent year. Since you don't know if information is available for 2007, it's best to search for a range of years using '..' as shown, or placing an OR between each year (less elegant).

Find the text for the poem At the Mermaid Caffeteria

an optimal query: "at the mermaid caffeteria"

Since the title of the poem is provided, it is safe to search for the exact string. Noting that caffeteria has a unique spelling, another optimal query would be not to use quotes at all. In either case, the top return is the answer. Unique combinations of keywords are often as effective as using quotes.

Information on a disc jockey named Bill Gates

an optimal query: disc jockey bill gates -microsoft

Bill Gates of computing fame is heavily indexed in Google. To find any other Bill Gates, you need to eliminate common keywords associated with the most famous of these that are not associated with the individual you are looking for. This is a particularly challenging search and other keywords may need to be eliminated carefully.