Currently, I have just one forum and I have no staff. However, a couple of years ago I was running multiple forums and I had a few staff. I used to give them cash for the work they were doing on my forums. My forums used to generate revenue Through Adsense and I used to keep 50 percent to myself and distribute the remaining to the staff. The monetary incentives my staff received was small but it at least something that gave me rights to demand them to post more and remain active on the site.
If you do not give any perks and if your staff is entirely made up of volunteers, I do not think you can get active staff. Having volunteers is certainly good because a community is hardly able to generate revenue but if all the staff are made up of volunteers, they might not be as much active as yo expect them to be.
Rewarding your forum staff is essential, in my humble opinion, since it will substantially boost your online community. Its success depends on their persistence, and rewarding them can increase the importance and fulfillment of their work. They will help in addressing particular problems in the forum, and they are more likely to stay committed to the community. Furthermore, they are more likely to support members' active involvement. You can give them a variety of rewards, such gift cards or premium memberships. Other choices include allowing them exclusive access to specific forum features and special forum badges or titles.
I don't currently have any staff, I'm flying solo. However, if I did have staff members I would probably reward them somehow, maybe 500 credits per month that they can use in our shop for their continued activity and contributions. If they had no use for the shop, I would try to find a different means of perks.
I have never had employees but clearly if I did all this is vital for the business to function, since in my opinion a happy employee is a good employee and being happy they work much better and more active so it is not only a good idea But it seems vital to me that the staff you have hired have good benefits that make them realize that it is worth working for you.
The first forums I ran, the staff were volunteers and didn't receive any form of payment. The only perks they really received were an additional rate of forum points they earned when participating on the forums.
In my large forum, when I eventually hired additional administrators, I paid them a small sum each month for their efforts. Usually around 25% of the sites' revenue for the month divided between the 3 of them, but frequently it was $100+ or so each. The Moderators were volunteers, but received increased forum currency for participating, and several of our volunteer staff received interest-free loans from us over the years for things like buying new computers.
I used to share Adsense revenue. I am going to start doing that again. I am also thinking about paying to post. Once I get my tech sites consolidated into 1 I will start some sort of revenue sharing for staff.
If I were to make money with a forum, I might consider "performance bonuses" for staff members. But we'd need to make enough to let the forum pay for itself and then some.
In the past, though, I've given gift cards out and even bought and sent things to my staff around the holidays.
I think anything you can do, to go out of your way to do, will be reflected on by your staff members.