Establish an atmosphere of trust. In order to get a man to honestly tell you how he feels, you need to have a track record of listening to him in a nonjudgmental manner. You also need to control your own reactions. If he shares his feelings with you and you begin crying or fly off the handle, you can bet he won't be opening up again anytime soon. If your relationship does not have a history of emotional safety during discussions, you may want to pursue counseling to address problems that can arise when one partner withholds feelings.
Have patience, and do not try to force the issue. No one likes being told what to do, and this is particularly true in regard to communication. Do not expect a man to communicate about his feelings on demand. Nagging is spectacularly ineffective in this circumstance. Let him know that you're concerned about him and would like to know what's on his mind.
Go for a walk or a drive. Not having to make eye contact can open the door to communication about touchy subjects. Walking is especially good, because your partner will not feel trapped in the situation. It is also relaxing, and if you choose a nice trail, beautiful. Being in a pleasant environment that does not remind him of past conflicts can go a long way toward opening the doors of healthy communication.
Realize that men like to fix problems, not talk about them. In her podcast "Celebrating Men and Sex," relationship expert Leslie Rice points out that acting as man's "problem solver" can help him to open up. When discussing your man's feelings about a situation, be sure to encourage him to include ways that the situation can be fixed. This makes a man feel competent and in control. Meandering conversations about feelings that ultimately don't solve a problem can be a man's worst nightmare.
Don't be too serious. Most men hate being told, "Do you have a few minutes? I'd like to sit down and discuss something." Statements like this can evoke feelings of dread and immediately put a man on the defensive. Instead, use humor to diffuse tension, if appropriate. Taking a casual approach to communication can be much more effective.