Rendering is literally an art! It's all about how much you compress it and in what format. Make sure your resolution matches the original file size (don't render a 720P file to 1080P, that leaves letter boxing which is wasted space unless desired).
I have a 6 minute video that is 720P at 60FPS (which really increases size) that is only 446MB. The original I believe is measure in GB! I should also add that it is nearly impossible to tell any quality loss from the original (it's actually an improvement since there is color correction and brightness filters being applied to the rendered videos).
I use .wmv (windows media audio/video), quality CBR (2 pass if you want a little better picture). VBR makes an extremely large file but for the best picture (that might not even be noticeable). Your bit rate settings also have an effect on file size and render time with quality being effected. All these options are under the advanced render settings.