While I'm on the usefulness of Web of Knowledge for grad students...

You can use Web of Knowledge to get a handle on the most important papers in a field you're just starting to dabble in (or discover important papers that might have slipped under your radar).  From the last post we saw how to search Web of Knowledge. After you land on the page returning the citations for your query, sort by "Times Cited." (Sorting options are above your returned citations.) You'll see a little arrow next to "Times Cited" -- down means most-to-least cited (selecting "Times Cited" again reorders from least-to-most). Voila! You have a list of citations from most to least cited. Of course, there are limitations:

1. This does not include books. The citations from your query are only what's logged in Web of Science. Admittedly, this is more journals than you can shake a stick at (and most of which you've probably never heard of), but just know that books aren't included. 

2. Any journals that aren't logged in Web of Science aren't included. My hunch is that journals that aren't logged are super obscure and likely aren't the best place to get up to speed on essential papers within your subfield.