To prevent ISPs from believing that they are under attack by a new sending IP with no sending history, it is important that you warm up your IP by sending small amounts during the first few weeks. This will help you stay under their radars until you build a good sender history. If you start to send in large amounts, the ISP will defer and/or eventually block your messages completely.
Always use your best data (most recent clickers) from your confirmed opt-in list. Send only what they signed up for to prevent your users from clicking THIS IS SPAM. The key is to engage your users. Within a month, you should be able to ramp up your delivery fully.