When I’m discussing the subject with YECs, quality is just about the only thing I focus on.
I tell them that it doesn’t matter how old they think the earth is, or who or what they think did or didn’t evolve from what. All that I care about is that they make sure they know what they’re talking about, and that their facts are straight — and that they make sure they’re approaching the subject honestly themselves before they start accusing “evolutionists” of dishonesty. After all, evolutionist dishonesty doesn’t reflect badly on us as Christians, but creationist dishonesty does.
Here’s one other piece of advice: suggest that they check out Reasons to Believe. I know that a lot of people round here will disagree with RTB’s stance on evolution, but I personally believe that RTB has a very valuable role to play in the debate. The fact is that evolution is much harder to understand than the age of the earth, and it takes considerable spiritual maturity and scientific expertise to understand what to make of it from a Christian point of view. Its status as a kind of political football in the culture wars is also pretty off putting too for many Christians. However, the falsehoods of young-earth are much more blatant and in-your-face, the age of the earth doesn’t have quite the same connotations in many people’s minds, and consequently there are a lot of YECs out there who are uncomfortable with evolution but who are quite receptive to the possibility of an ancient earth. This means that for an organisation such as RTB to be taking an old-earth stance without expecting them to accept evolution means that they’re not expecting them to run before they can walk.