I am using the "Internet Download Manager" from couple of years, and I can say with full of as-surety and with honesty that it is the best and easiest way to download any video from internet.
The best thing I like about this is, that if you have installed it in your system whenever you open any webpage which contain any video it shows you a link to download it in various form like(240, 360, 480, 720 etc). It is the easiest way to download a video on internet through "Internet Download Manager". I found only one issue in it, that is after some month it needed some key to open, for this you have to purchase it. Otherwise I really recommend this is a wonderful application to download the data.