Before I did my first direct examination of a real witness in a real trial, the partner I was working with gave me a bit of advice about leading questions that turned out to be very helpful. He told me that if the opposing lawyer objected that one of my questions was leading, I could probably fix the problem simply by asking the same question with the phrase "whether or not" tacked onto the beginning.
Here's an example. Say your question is "The light was green, right?" and it gets an "objection, leading" from the opposing counsel. Using the partner's method, the new question becomes "Can you tell me whether or not the light was green?" In some cases, the resulting question will still be deemed leading, but if the lawyer objects again, you're already on the right track to fixing the problem. That's important because in the heat of trial, it's often very difficult to figure out how to rephrase questions when met with repeated objections that are repeatedly sustained.
In my example, if the new question is met with another objection, it won't take much thinking to replace it with this one: "What color was the light?" The "whether or not" method is not only a handy crutch, but it also forces you to automatically think about what is was that made the question leading in the first place. While the leading nature of the questions I used as examples in this post is easy to see, in a real trial, things are often much more complicated.