Keywords in Product pages

Good day,
ia added <meta name="keywords" content="<?php echo @$meta_keywords; ?>" /> to common.tpl,
this variable gets value from db. So on index page i have keywords.
I want to products also have a keywords like:
manufacturer model
but cant get this values to common tpl (
How can i get it?

You need to add new column do product_description table, something like product_keywords and then add new form field to product admin section and do some php coding with validation, database stuff and then displaying in the template file. This should work.