Getting subscribers to fill out even a short form needs a strong reason, so you should promise them something valuable right after they submit their details. For example, ask a simple question on the form, like their biggest challenge in a certain area, and promise to send them a special checklist or guide that solves that exact problem. Make the form very short, only asking for necessary details like their name and maybe one quick answer, so it is not a big commitment for them. The quicker and easier the form is to complete, the more people will actually finish it before getting distracted. Do you think asking for just one piece of information is the best way to start?