Several of my clients have asked me to do performance tuning for their websites. I find it fascinating work, and rewarding to deliver improvements that help machines serve humans rather than the other way around.
I'll try to post nuggets of value as I come across them, regardless of whether they seem basic or advanced to me.
A great one to start with this first day is WebPagetest. It loads a page with an empty cache, then a filled cache in one of many browsers and produces amazingly detailed reports.
I have been doing a lot of tuning on one of my clients' sites, but mostly through my own Mac Chrome on a pretty fast connection. I had WebPagetest run the site on IE8 on a slower connection and got quite an education.