There are two ways of doing this, one way is to use torrent sites, like the Pirate Bay. This is NOT how I got my software.
In order to get my software, I simply went on Youtube and searched what software I wanted and put the word "free". You can also simplify your search my adding the OS you are getting the software for. Lets say I wanted Adobe CS4 for Mac, I would type in the search bar, "Adobe Cs4 free Mac". Now if you know about searching on Youtube like I do, you would know that it would simply some searching to find the right video.
Carefully read the full description of the video you are watching. It may have certain tips on how to get the Full software for free and certain directions you have to follow. Also, serials or links to downloads maybe in the description.
As dumb as this may sound, you should WATCH the WHOLE VIDEO!!!!!
Another tip is to read the comments and see if they worked. Usually if 1 person says it works, it usually works.
Also think smart...If you think a link is unsafe, don't click it..
In doing this, I was able to fill my Mac Hard Drive with Pro Software like Adobe's CS4 Master Collection (over $2000), Final Cut Studio 2 ($1000), Logic Pro ($400), Sony Vegas 8 ($500), Microsoft Office 2008 Mac ($200) and many more.
Remember, if its not on Youtube, use google and torrent sites. If you are on a PC, stay clear of viruses...