The right way to count from inside a match template

Dear All,
 I am sure this is a old chestnut of a question, but I just cannot get
it to work.

I have an xsl which is something like this:

<root>
<a><b>lots of stuff</b></a>
<a><b>lots of stuff</b></a>
<a><b>lots of stuff</b></a>
<a><b>lots of stuff</b></a>
<a><b>lots of stuff</b></a>
<a><b>lots of stuff</b></a>
<a><b>lots of stuff</b></a>
</root>

and I have a template

<xsl:template match="a">

<!--Show which element I on using-->

<!--display lots of stuff-->

</xsl:template>

For the <!--Show which element I on using--> I am trying various
different combinations
of <xsl:number value="something">

I have tried counting preceding siblings, position and several other
things, and I only ever get
a 1.

I would be really grateful if you could tell me What is the right way to
show 1,2,3,4,5 and then contents of each 'a4 element within the
template.

Thanks very much in advance,