Register Vkontakte its second page - let's call it professional, There give a maximum of information about you as a professional. In the status write to the service you provide to people, to strangers, it was immediately clear why you add them as friends. Now start to add people from your target audience. When the person you have friends, you can invite him to my group (though friends are added for some reason people rather than in groups)
Ask your friends to do the maximum repost their professional group. Sign up on sites where it is possible to perform simple tasks (liking, do repost, join in community, etc.) and earn points. Then these points to pay for that in your group screw subscribers. This method is good because it is fast and absolutely free, here's how people (bots are blocked). The only downside is that subscribers are random and not from the target audience as you would like.
Think of an interesting event with prizes. The point is that people do maximum repost and added to the group yourself, and then you, for example, by deposition of random numbers, will select three lucky winners (1, 2, and 3) Similar actions people are usually very interested and risk to try your luck. Go for it, you will succeed!