Gift subscriptions are a particularly great idea for niche hobby and enthusiast membership sites. You can position a membership as the gift for people who are tough to buy for. Email, search PPC and PR should all help givers know you’re the perfect solution to their problem.
Be sure to include guidelines about what will happen if the giftee already has an existing membership (it would be extended). Your marketing offer should be for a year (month-to-month doesn’t work well for a large number of reasons) and allow gift-givers to opt-out of auto-renew easily. Also, you’ll need special welcome (aka onboarding) campaigns to optimize giftee engagement in your site so when the time comes round to renew, they’re more willing to pay for it themselves the next year. Lastly, you’ll also want to implement renewal campaigns to the gift givers to remind them they can renew as well.