There's an easy way to use logical disjunction in a Gmail query. Instead of typing OR after each term, you can just use curly brackets and separate the terms with spaces. Here's the official way:
dan OR "brian clouse" OR teja
and here's a simpler way to write the same query:
{dan "brian clouse" teja}
Note that you need to use quotes for multiple words and you can combine the expression with other Gmail operators. To find all the messages sent by Dan, Brian Clouse or Teja, search for:
from:{dan "brian clouse" teja}
To find the messages that have one of the following labels: unread, starred and work (the first two labels are built in), use:
label:{unread starred work} (or: l:{unread starred work})
By default, Gmail uses the logical conjunction between your terms, so if you search for:
dan "brian clouse" teja
Gmail will display all the messages that contain Dan, "Brian Clouse" and Teja. To group these terms, use parenthesis:
from:(dan "brian clouse" teja)
Some useful queries:
label:(unread inbox) - the unread messages from your inbox
label:(starred chats) - your favorite Google Talk conversations
label:(unread muted) - the conversations you've muted that have unread messages
filename:{pdf doc xls ppt} - messages that have attached a PDF file or a Microsoft Office document
label:unread subject:{important urgent} - unread messages that include "important" or "urgent" in the subject.
{ credit for the magical-curly-brackets tip: Paul Buchheit }