How can I figure out what's slowing down my site?

[Steve]

The first thing I can see is that you load static assets from your meteor server. This is very slow. See here, for example:

First Visit Loads are Ridiculously Slow

Ever since one of the last few new versions of Meteor.JS, my application is ridiculously slow for first time visitors. I’m talking 10 to 20+ seconds for first time loads. However after I visit the application, all loads are fast and normal, even if I hit the refresh button. But once I clear cache and refresh again, first load is ridiculously slow again. Why is this happening? And what can I do to improve the first visit load time?