Once the wedding and honeymoon is over, you may be breathing a sigh of relief and hoping that life will become more calm and relaxing. And it should, but you will have one more time-consuming task to undertake - writing the "thank you" cards! Send notes of thanks as soon as possible after the honeymoon is over. That is when it's time to get down to business and begin your life together. And speaking of togetherness, both of you should work on writing the notes since you both were the recipients of the gifts.
Have some wine and make an evening of it and reminisce as you come up with thoughtful wording for each individual card. A simple, "Thanks for the gift" just doesn't cut it, neither does a pre-printed card - unless you also add a personal note with it. And don't forget to thank the members of the wedding party, officiant, musicians, etc., if you haven't already.
If you need some inspiration, whether you will be thanking guests for their gifts, or bridesmaids for all their support, I have an Example "Thank You" Wording page to get you started.