I agree with Mike that getting their feedback is important. Other characteristics that your plan must have:

* Simple - Don't over-complicate. Make something that is mostly straightforward and easy to understand: $X per conversion, %Y of all revenue during first 3 month ...

* Aligned - Make sure the plan is aligned for the current objectives of your business. Is your target to increase customers as fast as possible ? Then pay per conversion. Is your target increase MRR and reduce churn ? Then pay an increasing % of revenue over a number of months ...

* Immediate - Any plan your devise, make sure that sales people get the pain or gain as soon as possible (ideally monthly). Plans where pains or gains are further into the future don't incentivize as much as near real time ones.

Pere