It is not so simple to untwist group on social networks. If it was rather simple to publish interesting content earlier, then now the competition became incredibly big, and old ways lost relevance.
Direct ways
Cooperate with administrators of other groups. Write a request to private messages to arrange information exchange. Let's say you place advertizing about third-party group for some time, and her administrator - about yours. However owners of the untwisted groups will hardly want to arrange equivalent exchange with beginners. In this case you can suggest to place a post for day in exchange for several hours or to redeem advertizing.
There are even special exchanges which offer similar sale. The largest of them is Sociate. Here you will be able to find advertizing offerings on any sites. Let's say you need to untwist culinary group in Schoolmates. Just add several declarations and pay placement. The more qualitative it will be made, the more participants you will be able to receive.
Stage contests in the group. The prizes will be more valuable, the more people will want to participate in competitions. Standard conditions are some prize and the proposal to make a repost. The winner decides accidentally on the help of the special program. Only be absolutely honest, shoot a video where it is shown who exactly wins a prize. So you strengthen trust of users.
It is possible to order professional promotion of group also. You should not confuse this concept with wrapping. To you will bring the interested visitors who with pleasure will read your content, and in the second only bots who will not bring absolutely any benefit in the first case.
There are even whole companies which are engaged in similar activity, however it is possible to find also private performers. For search it is better to use the same forums and the exchanges of freelance.
Indirect ways
Publish as much as possible content. The users are more often see your posts, the more activity will be in group. Respectively, new participants will become more too. But do not forget about quality of materials. Information should be really interesting, useful and necessary. Also you should not publish texts alone. Load video, do collages of photos, organize polls, etc.
Order unique design of group. It concerns not only avatars, but the menu and other elements. For example, it is possible to create any character who will be displayed on all posts (it is valid, a deer at network of groups "Is overheard"). The necessary performer can be found at forums or the exchanges of freelance. Just place the order or select the ready offer.