The #1 concern most startups have is getting users without having to pay for them. Growth Hacking aims to accomplish this - and these strategies aren't silver bullets - you have to be a hustler and work at optimizing and tweaking them day after day. Sometimes this means doing things that aren't traditional, but always moral. You have to get creative and think out-of-the box. When everyone else is going one way, you go the other.
But for them to really be effective, you need to have a solid foundation in place so that all the work you'll put into spreading the word and getting lots of new users won't be incredibly hard or wasted on something people won't resonate with.