1. Try to take groups with more time off ( Although there is a second side to the coin ).
2. Run bots to dilute reports and make other users feel that the group is not so small, and that will not scare them away from unsubscribing. Keep an eye on the stats, control unsubscribes.
3. it is desirable that there is always activity in the group it - well influences it.
4. Start Start invite on small turnover 200-300 people. a day, do not rush to increase the audience at once, be patient, after a few weeks, when you see a good number of participants, you can increase your potential to 500-700 people. a day, but there is a small nuance in this case, never click from the account on the limits (up to 30 people), otherwise it can lead to block / ban the group.
5. Try to use accounts with more time to work and do not forget about good proxies ( TOR is not recommended ). Do not be stingy, because this is a responsible business when working with clients!