If you only want to change default sort order you can do it in catalog.xml just by adding the following action:
<action method="setDefaultDirection"><dir>desc</dir></action>
This action will work in any block of type “catalog/product_list_toolbar”, so the XML snippet would be:
<block type="catalog/product_list_toolbar" name="product_list_toolbar" template="catalog/product/list/toolbar.phtml"> <action method="setDefaultDirection"><dir>desc</dir></action> <!-- The following code shows how to set your own pager increments --> <!-- <action method="setDefaultListPerPage"><limit>4</limit></action> <action method="setDefaultGridPerPage"><limit>9</limit></action> <action method="addPagerLimit"><mode>list</mode><limit>2</limit></action> <action method="addPagerLimit"><mode>list</mode><limit>4</limit></action> <action method="addPagerLimit"><mode>list</mode><limit>6</limit></action> <action method="addPagerLimit"><mode>list</mode><limit>8</limit></action> <action method="addPagerLimit" translate="label"><mode>list</mode><limit>all</limit><label>All</label></action> --> </block>
This block is used twice in catalog.xml once for normal product lists and once for layered navigation product lists, so just make the same change in both places.
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<action method="setDefaultOrder"><field>entity_id</field></action>