Getting your needs met when relying on others can be a huge feat. Especially In the real world. We tend to overcomplicate matters by beating around the bush, being passive aggressive, or simply hoping others will read our minds. That rarely works in real life and even though I don't have an exact statistic, I know it doesn't work online.
In the online world (unlike the real world), people like to be told what to do. Not because they're stupid, but because they're looking for a next step with you when you or your brand appeals to them. So it's best to be direct, straightforward and get to the point. Quickly.
Do you want them to give you their email? Ask them for it.
Do you want them to opt-in for your freebie? Tell them why they need it, make it irresistible and offer it up.
Do you want them to buy your product or service? Give them a big BUY NOW button.
Do you want them to leave you a comment? Ask them for feedback.
Bottom line...tell people what you want them to do. And the best thing about doing it online...you don't have to hear any pushback or gripes. People will either comply or move along in silence. It's a win-win.