I have a list of nodes that I can select based on a criteria. But I need only a specific number of them. For eg. a criteria may return 10 nodes but I just need to select the first 6 nodes. How can I do this. I need to do this for pagination in FO.

You can use a predicate and the position function, for
example
 <xsl:apply-templates select="item[position() &lt;=6]"/>
will apply templates to the first six item elements.