Generally it is done by promoting it. Facebook, Twitter, etc are all good sites to push projects on. Upload a lot of youtube footage of alpha, possibly try and involve the community. Remember to fake footage to some degree with impossible or experimental mechanics as the more impressive something seems the more hype and attention it gets.
If your project is just a WC3 map then do not bother as very few people still play WC3 and those that do have a huge library of maps to choose from.