When you've built up a bit of rapport with a subscriber, you'll start to get a feel for when they might be ready for your next offer. Pay attention to how engaged they are with your content, how often they purchase from you, and whether they seem interested in what you have to say. It's also important to remember that not everyone is going to be ready for your next offer right away - some people might need more time to warm up to you before they're willing to buy something else from you. Just stay patient and keep putting out great content, and the rest will fall into place.