I do my own hosting for a few clients on my own VPS server (Lindode). Since my clients so far have been extremely low traffic, I have not had to really dig into some of the considerations that I would need for a higher traffic site. Now I am bidding on a client whose site will be potentially higher (not Facebook or twitter, but higher than Joe's ice cream shop). Is there a list of things I need to think about that I may be missing?

I am going to assume, at least at first, that I will be able to handle them on my shared Linode, but I could move to a dedicated Linode if need be. I am not thinking so far of multiple servers, but short of that there are still considerations. For example, mod_perl instead of straight CGI, better backups, etc. What else?

In case it matters, the stack will be debian-linux / apache / Perl / mysql / Template Toolkit.