This is a post for Creationists who want to be honest. Of course, many of my readers will probably mentally snark along the lines of "there's no such thing!" as they read that first sentence. That right there is one big problem you will have to overcome: We've seen so many Creationists who seem prone to compulsive lying, that it's become a default assumption for many of us. Because of that, you'll often need to put some extra effort into your appearance of integrity. After seeing so many ways to not do that, I think I can make some suggestions on how you should approach a skeptic:
1. Know that many of those on your side are dishonest, and that you may have been fooled by one of them: There are a lot of dishonest questions, assertions, and so forth floating out there in the internet that have become detached from the liar who started them. Ask about things as honest questions in as soft a tone as you can manage. Many of us skeptics are veterans of these debates and will probably have an answer. If the skeptic points out the source of the lie, try to be gracious in response.
2. Ask honest, basic questions: By this, I mean ask about very simple concepts and definitions. Aside from the aforementioned "urban legend" deceptions, there are many misunderstandings of what the theory of evolution, abiogenesis, and the Big Bang actually are. Before a debate can really begin, you need to know what your opponents are actually arguing about. Otherwise, you're just ridiculing a straw man.
3. Don't use quotations: The dishonest Creationists absolutely love what has become known as "quote mining": The practice of taking a quote out of context to make something sound ridiculous or contrary to what a person actually believes. Darwin himself was particularly vulnerable to this because of his rhetorical style: He would raise an objection he expected opponents to make and then rebut it. Dishonest Creationists would then clip off the rebuttal and make the quote about the objection viral.
4. We don't really care about Darwin that much: This may come as a surprise, but as scientifically-minded people, we don't particularly care about Charles Darwin in terms of science. We only care about him from a historical perspective. Science is a self-correcting process, and the more we study a topic, the finer details we are able to examine and understand. We appreciate Darwin for getting the broad concept right, but no serious scientist would use the Origin of Species to research the answer to a modern question. It's essentially the same as with Newton: We can use Newtonian physics to answer some simple questions about the "medium world," but when dealing with super-massive objects, objects traveling near the speed of light, or tiny particles and quantum events, we need to refer to more modern theories about the things Newton did not yet know about.
5. Don't say "Darwinist": As said before, we appreciate Darwin's contribution to biology, but putting an "ist" on the name is a propaganda tactic popular with dishonest Creationists. They do this because they try to dismiss the science as a form of priesthood with Darwin as a saint or a prophet. He was not. We can look at the world and see the effects of evolution. Darwin was just one of the first people to figure it out and express the concept clearly. That's all Darwin is to people like me. He wasn't a saint or a prophet. He was just a guy who happened to have the smarts, luck, and data to put together a useful explanation for the diversity of life that modern scientists could build on and improve.
6. Credential don't matter: Though many of my fellow skeptics like to ridicule Creationists who tout their PhD's from diploma mills, I don't believe credentials matter: A valid point is a valid point, no matter how many letters its speaker has after his name. Credentials are merely a way of saving time in evaluating someone's opinion. When you're discussing the topic in detail, it's best to drop such distinctions and take your time to work out the quality of the evidence and the logical steps from there to conclusion.
7. Don't pretend to know us: Deception is rampant among Creationist circles, so do your best to remove any prejudices you may have developed as a result of viral arguments. Skeptics like me often have to face "woos" from many fields who treat us like stereotypes from Hollywood and network television without ever knowing how or why we've reached our conclusions, or what it takes to change our minds about them. Even if you think we're mad, there is a method to our madness.
8. Look back and remember: One way I've heard to spot a chat bot is to ask what it was talking about earlier. I sometimes feel like accusing dishonest "woos" and Creationists of being such when they can't remember an earlier rebuttal or present an argument that contradicts one of their earlier ones. Too many attempt to play "gotcha" instead of learning and adapting. Try to show that you're learning about our side of the argument. If you spot what looks like a contradiction, ask if there's an explanation, an exception, or whatever. We can make mistakes or oversimplify things. We might even learn something new if we have to look up an answer or correction if we didn't realize the mistake.
9. Don't cite faith: Many of us are vehemently opposed to the "accomodationists" who talk about reconciling faith and science. By "faith," I mean belief without or in spite of evidence. Belief without basis is essentially an act of hubris. There needs to be justification for a belief, and in science, that comes in the form of evidence and logic: The evidence must agree with your premises, and your conclusion must logically follow from those premises.
10: Do your homework: Read up on logical fallacies to avoid and existing rebuttals to common Creationist claims. Yes, I realize this may take up a lot of your time, but if you can learn more about us and our arguments, you'll be better equipped to discuss the issue. A great deal of frustration we experience is having to rebut commonly repeated arguments. If you find an answer confusing or even ridiculous, politely ask for elaboration or clarification while providing a link to it. People like me will appreciate your efforts.
Though my skeptical friends and I are known for having sharp tongues, if you practice these things while doing your best to maintain a polite tone, we're much more likely to be civil in response. A great many arguments fall into trolldom when someone violates these sorts of 'rules'. In many cases, they don't even realize why we react so negatively to the behavior in their first post. I'm not vicious by nature, just sensitive to perceived injustice, deception, and apathy. Honest curiosity is a beautiful thing that can tame this copper alloy canid into showing off the tricks he knows. I enjoy putting effort into explaining things if I believe someone is interested in hearing it.