Ours is rank based so the more referrals to the waitlist the higher your rank the better offer you’ll get I.e Augustapp.com free for X months etc.
We’re seeing good results from it so far.
Honestly there are so many different approaches you can take to get people to join your waitlist and I suppose it depends on the stage of development you are at. But early on we found simply interacting and building relationships in the communities where our target audience hangs out really fruitful, not just in getting sign ups on our waitlist but, also doing early product demos for people and getting their feedback. Doing everything you can to interact and build relationships with your early customers is key from our experience.
A piece of simple landing page advice I got from a bootstrapped founder who exited his micro-saas for multiple 7 figures was:
1. Call out your ICP
2. Call out 1 problem you're solving
3. Give them a reason to enter email (discounted lifetime rate, free trial, etc.)
I've found that if you nail 1 and 2, 3 doesn't matter as much. But that's been my experience!