One important thing to learn when defending any position is to learn how to do it in an orderly, convincing, and coherent way. One's ability to do this often comes out in debate, or in their writing.
Love him or hate him, William Lane Craig is an excellent debater who wins most if not all of his debates on existence of God. That's why he is a great person to look at to learn how to debate, even if you passionately disagree with him. Here are some things I noticed when watching his debates and talking to other people about them (including atheists) that make him a really really really good debater.
1) Know your stuff, really really really well.
This kind of goes without saying, but its hugely important for winning debates and being persuasive. As for William Lane Craig's Kalam Cosmological argument, he debates it in scholarly philosophical journals. However, many of the people who want to debate Craig in public underestimate how much he knows about his own argument, and are not philosophers themselves. So whenever they raise an objection, Craig already knows how to respond to it. This is a great skill to have no matter what position you are defending. In fact, Craig knows so much about his argument he is able to write an entire book and then a 100 page article on 3 sentences (his three premises). Agree with him or not, he certainly knows his argument, why he believes it, and what objections can be raised against it.
2) Have more than one argument for your position
William Lane Craig has been using the same opening speech in his existence of God debates for over 10 years. He usually has 5 or 6 different arguments to support his supposition that "God exists." These are set up as syllogistic arguments. Nevertheless, each premise in each of his 6 arguments itself has many supporting reasons. For example, one of the premises in the Kalam Cosmological argument is "The Universe began to exist." Craig has at least three sub-arguments for why that is true. He even sets up the sub-arguments in a syllogistic fashion. This way, the opponent has to tear down all 6 arguments for the contention "God exists" and has to tear down all of the sub-arguments for at least one of the premises in each argument. As I said before, love him or hate him, but a brilliant debate tactic. On the flip side, it is extremely important to not have your entire position depend on just one argument. This is what Stephen Law did in his debate with Craig, and I think it was a really bad idea.
This also works when responding to objections. If possible, always provide more than one reason why the objection is wrong.
A caution here. You have to be careful how many arguments you use in a debate, or its considered rude. For example, if Craig just listed off 40 syllogisms and expected the opponent to tear them all down, that would be rude and unproductive, especially when trying to persuade an audience. You need more than one or two arguments, but less than so many that its distracting and disorganized when the opponent goes to respond.
3) Dismiss or Concede Irrelevant Objections
When debating his opponents, Craig often concedes things that do not relate to one of his objections. For example, in his debate with Antony Flew, Flew brought up that Craig's God is unjust, because he uses eternal punishment. Craig responded by saying that they were just debating the existence of a generic monotheistic God, not the Christian God. (However, Craig did respond to the objection, since he is a Christian theist.)
Same applies to things like evolution, or Biblical inerrancy, or anything else that sounds like a rough objection on the surface. In most debates about Christianity, things like evolution and Biblical inerrancy are irrelevant objections. What does evolution have to do with whether or not Christ rose from the dead, or that a God exists? What does inerrancy have to do with whether or not Christ rose from the dead, or that God exists? We trust historical sources all the time, even though they sometimes contradict each other. So inerrancy doesn't even matter when proving Christ rose from the dead. These are moot points in the overall picture of things. So, make sure you do not get bogged down in difficult or distracting objections that do not necessarily relate to the contention at hand. The objection may be a good question to ask, but don't get distracted to it when it doesn't relate to one of your arguments.
4) Be very clear when presenting your argument.
As I said before, Craig presents all his arguments in syllogistic form. This way, it makes it very clear where the opponent has to disagree and what Craig has to defend. One does not always have to use syllogisms to be a good debater or to be clear, but it is certainly a good idea for some things. Nevertheless, the overall idea of being clear in the presentation of your argument and laying all the relevant components of it out on the table is a very important lesson to be learned. Furthermore, your overall structure should be very orderly and something one could easily turn into an outline or bullet points.
5) Use Clear Analogies to Illustrate the Force of Your Point
Analogies are not arguments in themselves. But they are a great way to drive home the force of a particular argument. Craig's "Hilbert's hotel" and library illustrations are great ways to illustrate why he thinks its impossible for an infinite number of things to exist in reality. Having good analogies are a great way to help your point sink in with your audience, and to help them understand why your point is so powerful.
6) Use Facts that Are Agreed Upon by Scholars in the Relevant Fields
When debating the existence of God, Craig does not appeal to possible flaws in evolution for his design argument. Creationism is rejected in most of the scientific community. (Craig is himself undecided on common descent.) However, he does point to cosmic fine-tuning as evidence for design, since the scientific community accepts cosmic fine-tuning.In addition, when debating the resurrection, Craig does not appeal to the guard at the tomb or doubting Thomas to prove his point. He appeals to facts that are accepted by the majority of historical Jesus scholars. This is an easier way to debate and makes your argument stronger.
So we have seen why Craig is such a good debater. These skills are useful in defending any position, but particularly so in defending the Christian faith.