You may have noticed that Twitter is very celebrity-focused; at least for awhile, it was more likely to suggest that new users follow a Kardashian than their friends down the street. That's changing, however. CEO Dick Costolo tells those at a Goldman Sachs conference that he plans to revive the social network's slowing user growth by encouraging newcomers to get involved. Twitter is reducing the number of steps it takes to sign up, and it's suggesting people who are more likely to follow back, such as phone contacts. Not that Costolo is betting everything on that one approach, though. The company is also experimenting with more ideas, including additional cards and commerce. It's too soon to tell whether or not the chief executive has the right idea, but it's safe to say that he doesn't want Twitter to stand still.