Add documentation about flushing and flags.
diff --git a/glog.go b/glog.go
index e951593..2d36acd 100644
--- a/glog.go
+++ b/glog.go
@@ -32,6 +32,37 @@
//
// glog.V(2).Infoln("Processed", nItems, "elements")
//
+// Log output is buffered and written periodically using Flush. Programs
+// should call Flush before exiting to guarantee all log output is written.
+//
+// By default, all log statements write to files in a temporary directory.
+// This package provides several flags that modify this behavior.
+//
+// -logtostderr=false
+// Logs are written to standard error instead of to files.
+// -alsologtostderr=false
+// Logs are written to standard error as well as to files.
+// -stderrthreshold=ERROR
+// Log events at or above this severity are logged to standard
+// error as well as to files.
+//
+// Other flags provide aids to debugging.
+//
+// -log_backtrace_at=""
+// When set to a file and line number holding a logging statement,
+// such as
+// -log_backtrace_at=gopherflakes.go:234
+// a stack trace will be written to the Info log whenever execution
+// hits that statement. (Unlike with -vmodule, the ".go" must be
+// present.)
+// -v=0
+// Enable V-leveled logging at the specified level.
+// -vmodule=""
+// The syntax of the argument is a comma-separate list of pattern=N,
+// where pattern is a literal file name (minus the ".go" suffix) or
+// "glob" pattern and N is a V level. For instance, -vmodule=gopher*=3
+// sets the V level to 3 in all Go files whose names begin "gopher".
+//
package glog
import (
