Advice for running an ecommerce site

A user on Ubuntuforums is asking for advice on running an E-commerce site. Mregister asks:

i am new to ubuntu/linux and was just hired as a tech guy for a small company. they are putting their catalog online and are putting an ecommerce site together. they have hired a consulting firm to build the site and it is going to run on an ubuntu/lamp box which i am going to adminstrate. Yikes!! I have for the last couple of weeks built a test sever and installed ubuntu 8.04 with the lamp configuration and added openssh, ssl, and have played around and have become somewhat familiar with navagating around ubuntu and various config files and such. i have setup and then broken openssh, public/private keys, etc. anyway, when i build this thing for production what areas do i need to pay specific attention to? what advice can you guys give me? i have no help except you guys here and i am not even sure what questions to ask. any advice is much appreciated.

Seeing how Slashdot is a wealth of knowledge on this topic. Let's help mregister out.