Bit of an open-ended question as it depends on how much you know about the Actinic Templates. There's plenty of info in the supplementary Design and Advanced user guides downloadable from here:
You could start by looking at Design>Options>Layouts>Default Product Layout. This allows you to specify a default layout for ALL your product pages. Click the edit button to edit the template.
You can also modify product the template from Advanced>Template Manger>Sections>Product Line.
You can specify different product layouts per section by going into each section, selecting the Product Tab and specifying a Default Layout template.
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