In general, and for nearly any such situation with a loved one, you should always keep in mind the golden rule. Practice a a measure of empathy and put yourself in your spouse's shoes: How would you want your spouse to tell you, for example, that your kissing practices are not satisfactory? Would you want them to get frustrated with you and blurt out, "Ugh, you kiss like a wet fish!" Or would you want them to lovingly and compassionately take you in hand and guide you in the right techniques, to communicate open, honestly and with great sensitivity?
By the same token, your spouse will want/need to know the truth, but presentation of what you think and feel can either be harsh or with compassion. Don't do this out of frustration or impatience -- instead, speak the truth in love.
