The specificity is the whole design. A general guide to your industry attracts students, competitors, and the curious. A calculator that tells somebody what their specific situation will cost, a checklist for a decision they are making this week, or a template that saves them an afternoon attracts people actively dealing with the problem you solve. Fewer signups, better list, and the second is what matters.
Make it something they use rather than something they read. Completion rates on downloaded documents are poor and a document nobody opened builds no relationship. Tools, templates, checklists, and calculators get used, and using something you made creates a considerably stronger impression than reading something you wrote.
Keep it small. A comprehensive resource takes weeks to produce and performs no better than something that takes an afternoon, because the value is in solving one problem completely rather than in covering a subject. The most effective ones for a small business are frequently a single page, and the effort is better spent on making it genuinely correct than on making it long.
Ask for the minimum at the point of exchange. An email address is enough. Every additional field reduces completion measurably, and the information you were going to collect is available later in conversation once somebody is engaged. A form asking for name, company, phone, and role is a form that gets abandoned by people who would have converted.
Then deliver what happens next deliberately. The first message should provide the thing immediately, and the second should follow within a few days with something related rather than with a pitch. A lead magnet with no sequence behind it collects addresses and produces nothing, which is the most common way this effort is wasted.
Test whether it actually delivers before promoting it. Sign up yourself, from a different email address, on a phone, and confirm that the message arrives promptly, that the link works, and that the file opens. A meaningful share of lead magnets fail silently at one of those points, and the business never finds out because the people affected simply leave rather than reporting it.