Text never takes up too much KB size, so you shouldn't have to worry about that too much.
Normally the elements that slow down a website the most are the graphics, that is banners and images. So it's essential to optimise them (reduce file size (KB) without degrading quality too much), you can use an image editor like the free GIMP or PhotoShop Elements to do that. Unless you are doing a portfolio site for say wedding photography, aim for you images to be be lower than 40kb.
Media (Music, slideshows etc) can also slow down the download time of a webpage, so it's important to minimise their usage on the home page, and to optimise and best as possible on other pages.
Call to external reference, such as FB, Twitter feeds, Google Analytics should all be done at the last possible moment to allow the page to load first.
There are site like SEO Optimisation where you can input your website and it will tell you the page weight and how much each element is contributing to that. You can also use the PageSpeed extension/plugin for FireFox and Chrome.
IMHO it's better from a visitor point of view to see a page loading, than to halt the page until eveything has been pulled across the internet and then displayed. It can be done but it woul dbe counter productive.