Launching a brand new service, subscription based B2C market. How do you incentivize members to purchase your annual membership over monthly, and secure your profit without worrying about churn?

My product will be $3.99/mo or $39.99/yr - obviously the $8~ savings for the annual membership is one perk.

How do other companies push annual subs and what works for you? I’ve considered offering raffle / contest entries for annual subs - or an additional $5 discount on the annual sub for the first 100~ subs, but want to hear what truly works before committing!