Really listening and letting your partner know you've heard is the most important communication skill.
Most of us want to answer, to tell what we think, but listening means not giving your opinion. (At least not until your partner really feels heard. You'll give your thoughts when it's your partner's turn to listen.)
Best way to do it is to basically repeat back what you heard, and ask, "is that what you said?" Listen for what's important, feelings, needs. Ask open ended questions inviting your partner to share further and fully. Resist giving your opinion - even when you completely agree. Make it about hearing your partner's opinion. This is especially important if you are communicating about something difficult, emotional, or when you disagree.
Listening with acceptance and love is the best gift you can give your marriage.