Every project try to gather as many user attention initially. They usually look out for audience who are crypto related which they can find on forum sites like Bctalk and other forums. They either try to capture that with Bounty or simply press release on any of news sites.

IMO investing in only specific advertisement options ( like say press release, banners on crypto related sites etc. ) is very cost efficient but less effective than investing in a program packed up with multi-platform advertisement (say bounties) which is expensive but is most of the time effective.