Something your target audience actually want.
I repeat — your target audience must want it. Otherwise, don't even waste time creating.
To achieve this, you need to know who you want to serve (again target audience) and the problems they’re trying to solve. Figuring this out is outside the scope of this guide.
Once you’ve discovered their problems, list them out.
Choose 1 PRESSING problem and create a lead magnet to solve this specific problem. You don’t want to solve all their problems because you’d have nothing left to sell to them.