Online store - where to start - planning

I have a website and wanted to implement a database and shopping cart software.  Can someone please give me some pointers on how to plan it efficiently,

what features I would want to have for it and some general info.  point me to a tutorial online, a great book or vid or anything you think might help.

It would be great for some feedback - this is important to me.

Cheers!

Hi, what sort of site do you have now?  There are loads of really good off the shelf open shopping systems.  We really like the prestashop model but whatever mode (assuming you are not writing from scratch) ban easily be installed on your site via a folder or as a subdomain.

I have an online store with a static website attached to an interface that processes payments via pay pal - it's crude though.

[ http://www.companycasuals.com/allapparel/start.jsp ]

I wanted to have a dynamic site - the products stored in a database searchable and customizable on the administrative side, the shopping cart and payment gateway.  I really want the site to look and act professionally.

I am trying to get the data base set up so I can display the products as I choose and really get it going.  I know very little about setting it up with PHP and MySQL.

I am past the point of planning now - I have the DB that I need to use, have redesigned the website and have started to make the pages to display the products.

How do I use PHP and MySQL to display the products?  I am starting to figure all this out but tips would be helpful...

Thanks