First step of optimization is file minimization. (I strongly recommend GULP for minimization and optimization. Its simple watch solution, installation and all files are compressed at once.Supports all CSS, JS,less, sass, etc...)
OR Old school solution:
In general if you want, as a process of optimization, to optimize a site performance, try merging all CSS in one file and compress file by using Compass. That way your multiple requests to static CSS will be replaced with single one.
Problem of multiple JS you can resolve by using CDN (or Google Hosted Libraries) so requests go to other server not yours. That way server doesn't wait for previous request to complete before sending next.
If you have your own locally stored JavaScript minimize each file by using Brackets plugin "Compress JavaScript". It's basically one click to compress JavsScript.Brackets is free editor made for CSS and JS but can be used for PHP and other languages. There is plenty of plugins to choose made for both front-end and back-end developers. In general "one click" to do all these (so far multiple) commands. Btw, Brackets replaced my very expensive Dreamweaver ;)
Try using tools like Sass, Compass, less to minimize you CSS.
Note: Even without using SASS mixing or variables your CSS will be compressed (just simple use pure CSS and Compass "watch" command will compress it for you).
I hope this helps!