Research alternative greeting card subjects, as not every writer has experienced them. For instance, if you are writing a congratulatory "quit smoking" card, but you have never smoked, you may not have a firm understanding of just how difficult quitting is. Read firsthand stories of people who have quit smoking, and tailor your verse writing with their experiences in mind.
Write sentimental alternative verse in unrhymed conversational prose. Conversational prose is also known as the "me-to-you" voice that we commonly see in many of today's popular Blue Mountain Arts or Hallmark cards. Write as if you are having a conversation directly with the reader. Use fresh, yet colloquial language, and avoid overused phrases like, "You mean the world to me."
Write cheerful alternative verse in a humorous vein. Humor is the most popular greeting card style sold today, ranging from simple puns to the downright outrageous. Use your judgment when writing humor as it may not be appropriate for every subject, such as terminal illness. The key to a successful humor card is originality--write something that hasn't been written before.
Keep your messages hopeful, whether written in conversational prose or humor. Greeting cards are meant to evoke positive emotions in people. In cases where the subject is dire, offer supportive words of friendship, prayer or love.
Browse the store racks to find out what kind of humor is currently selling. To get your muse going, look at illustrations on humorous cards and think of what you would write for verse. Photographic prompts are a great way to come up with original ideas.
Read your verse out loud to an audience, and study their reactions. Do they give a happy sigh or laugh? If so, you are on the right track. If your listeners don't get your joke or if your verse makes them feel sad, scrap it and start over.
Familiarize yourself with current greeting card trends. The more you do so, the better your writing will get. An excellent book on the subject, which includes plenty of tips and idea joggers, is "You Can Write Greeting Cards" by Karen Ann Moore. Also, the Greeting Card Association has a very informative website (see Resources below).