Small ask, get them using your software/service, then start a dialogue with one of your pre-sales... "Hey, great to hear that you signed up for the trial, how's it going, what are you using it for, who is your CFO by the way?"

It kind of depends on your service though, and who will be using it. Tech types are more wary of long forms and prefer to be contacted by a tech person; opposite for biz types who have a problem to solve and a boss leaning on them.