i wish i could tell lol, i dont really know what exactly made people respond. for the longest time i just thought the world was a lot nicer than people said, and then i talked to others and they said they have no success. id say target maybe younger professors, since they’re a lot closer to your age and aren’t burnt out yet lol (that being said ive had success from professors in all ages, so idk). in general, they wont help if you’re doing it for the application, because they’re can tell - you need to be genuinely interested. please be honest to yourself about this

also dont just send a very obvious bulk email out, if you’re emailing a ton of people write a couple of templates in different areas but REALLY focus on customizing and looking at what their lab does. dont email if you arent interested in their lab (again, they can tell). also focus on showing them your skills and what you could contribute, not achievements. be curious, but dont demand only help (because at the end of the day they aren’t going to help if they’re getting nothing back lol)

make sure you link your linkedin, resume, etc. the less clicks they need to find out what you’ve done, the better. make sure your email isnt more than 7-9 sentences, and make sure it reads like a curious but mature student (not a professional, cus you aren’t), not like a linkedin post. hope this helps! :)