1: Avoid to External links like youtube video you can use image and play vide in lightbox check lightbox example.
2: Avoid heavy images (optimize images as per google instruction).
3: minify js, css, html.
4: add expire header
5: use chache plugin fastest cache plugin is good.

1: Avoid to External links like youtube video you can use image and play vide in lightbox check lightbox example.

I’m not sure how that would speed up a website. It’ll probably introduce at least 2 extra http requests and consume more processing time.