I would draw a distinction between dating and going on a few dates. Going on a few dates to see if you like someone romantically, deciding you don't, and declining to go any further, is not leading them on. Getting involved in a relationship with someone you aren't attracted to, because they look good on paper, or because you hope that sparks will develop is leading them on.
I think it also depends on how well you know someone. If you've known someone for a significant amount of time, and there's nothing there, dating them probably isn't going to change that. If you've met someone for five minutes, it's going to take a date or two to find out, unless the first meeting was really spectacular. So if your best platonic friend has a massive crush on you, and you don't reciprocate, then agreeing to a few dates is not going to help, and is probably going to make things worse.
As far as self knowledge goes, I also think it's worth paying attention to whether your 'sparks' give good advice. If your initial attraction tends to lead to relationships that quickly fizzle out, or go bad, then it's worth stopping to reconsider your dating criteria. I suspect that a lot of us have had that friend who, after a string of disastrous relationships, complains that they never meet any nice men, and we have to bit our tongues to keep from telling them that they meet tons of nice men, they just dismiss them within a few minutes of meeting them as boring and not attractive.
It also helps to not complain or comment on having trouble meeting people around people who have unsuccessfully tried to set you up or suggest people, for the sake of both sets of people.