My favorite way, which I haven't gotten to use yet because all the pregnancies came at REALLY bad times (read: best times for the glory of God to be revealed in our marriage and family!), but what I'm planning on doing with the next:
I plan to wait til I'm three months along in case of miscarriage. Once there, I'm going to get a babysitter, fix a romantic at-home dinner on a date night. Everything will be "baby"....baby peas, baby carrots, baby potatoes, baby asparagus, caviar, baby desserts, etc. You get the idea. Then at the end of the meal once my husband's done raving, thank him and ask him what the meaning of the meal was. This will both (a) calm his hormones enough so he can use his brain and (b) get him scared that there's something important he's missing and what could it possibly be? Then go through hysterics and theatrics, demonstrating mood swings, making reference to nausea, saying it took so much out of me all I want to do is sleep.... etc. THEN once I've got his goat, return to "normal" in my speech, body language, etc, thank him for his attendance and participation in my performance, and ask him what the "theme" of the night was. I'll drop clues and if he still can't guess I'll suggest that it's time to get the Comfort-U body pillow out of the attic again. At this point he'll totally get it. :)
Just a fun idea. Good luck!