I find that making the very last sentence a question makes it much more likely that I'll get a response than if the question is anywhere else in the email. The person needs to finish reading the email with the question, which prompts them to hit reply and answer it.

The immediate-response-rate goes down even more if the input being sought is not framed as a question ("I've been trying to figure out how to handle this situation" versus "Which do you think is the better route?").

Of course, some people will still respond regardless, but I've found that in both personal and business emails, keeping an email short and finishing with a question mark is the best way to ensure a rapid response.