Should you and your spouse engage in pillow talk when your heads are on the pillow?
Most people don't communicate about sex in general, much less when they are in the middle of it. There are some reasons for that. You could be afraid of your husband or wife getting angry and interpreting it as criticism. You may also be worried about making them feel inadequate or spoiling the mood. Or, you may simply not care about pleasing your spouse (yes, there are people like that out there). But generally, I think that while you're having sex is not the best time to be talking about it.
There has been significant research showing that non-verbal communication while having sex is a lot more effective and fulfilling. "Non-verbal" means the way your body moves and the sounds you make (e.g. the moaning and the groaning, the "Yes, that's good, a little more to the left...Oh, that's fabulous," and the "Let's try ___"). Even though you're speaking, it's not really verbal - you're just egging on the situation.
However, it is still very important for married couples to talk about these things because it leads to more satisfaction in their relationships.
So when is a good time?
When you're not in the bedroom.
At some point in the near future, say to your spouse, "You know when you did such-and-such? That really turned me on." He or she may not even remember that they did it, but it doesn't matter. It's really important that you give each other positive strokes - literally and figuratively. It should all be enthusiastic, and none of it should be critical. The second your statements start turning critical, it's over. Your spouse will realize that they didn't please you, or even worse, that you've been miserable for a very long time.
In addition, when you are talking about it, try saying something like, "Oh yeah, honey, that felt good. Do you want to try doing ____ while you do that? I think I'd like to know how that feels." In other words, you're not critiquing your spouse - you're exploring your own body.
Husbands and wives are usually enthusiastic about pleasing each other, and yours will most likely be willing to try something out (unless you're asking for kinky, weird stuff). Just remember, people who communicate their enthusiasm, interests and positive reactions have more fulfilling sex lives with their spouses.