The above methods are what can bring you the most subscribers in the least amount of time, but there are still other ways that you can build a list, so I wanted to still mention them.
List building methods that use blogging, social media (Facebook, Twitter), and YouTube videos, are fantastic ways to help supplement your overall list building, but they are not the quickest ways to go about list.
You can build a big list using a blog to attract traffic, having your opt-in form on the side of your blog. But the problem with blogging to build a list is that you need to spend time to build up traffic to your blog. It will most likely take several months before you can start seeing a significant amount of traffic, therefore it will take even longer to build up a nice size email list.
Facebook and videos are similar. You can build email lists with them, but you will not see immediate results. You will need to first build up a following in Facebook and YouTube and then redirect visitors to your squeeze page to add them to your list.
What I would recommend would be to use these other methods to help build your list in the long-term, don’t do it for quick results or else you will be disappointed. Realize that your overall marketing efforts should contain these other methods (and others too) for the most impact in the coming months and years, but if you are trying to build your list to 1,000 subscribers quickly, then focus on the first mentioned methods.