Summarize the following:
The Greeting Card Association (GCA) has a listing of members that accept submissions from freelance artists. You will need to contact them first before sending in any samples or submissions. The contact information listed there is only for more information. Industry journals like Artists Market also list opportunities for freelance graphic designers who create greeting cards. Individual companies have specific guidelines for submitted artwork, including format, size, and medium. They will also have a specific address or person to send submissions to, which may be different than the person you contact for information. Make sure you are familiar with each company's guidelines before submitting something to them. Create cards that correspond only to what they ask for as far as genre and themes.  Make sure your submissions include your name and contact information. For artwork, be sure to include a copyright on your work as well. If you would like to have your work returned, include an appropriately sized, pre-addressed, stamped envelope for the editor to use. Some companies, especially those with a certain mission, are looking for specific types of card designs. These can be themes that the company promotes, or certain popular events that people like to purchase cards for. Stay on message. When designing, look at the type of cards they produce, and how those materials will affect the medium you are working with. When submitting, think about the type of company you are submitting to. Larger companies will have diverse demands, but you will face stiff competition. Smaller companies can have a tighter focus on what they want, but will be more likely to gain acceptance as long as you fit their niche. Some designers like to start with smaller companies to get some work accepted and create a reputation, building to the biggest buyers. If you get denied by one greeting card company, move on to the next one. This is a business, so you can't take criticism personally. Don't be afraid to make changes suggested by editorial staff or other feedback they give you. Each company treats its freelance workers differently, but in most cases cards are accepted on a flat fee basis. If you are proposing a line of cards, then you may be able to negotiate royalties, or an advance against future royalties.  If you are submitting text, the company will likely purchase your work outright for a flat fee (usually somewhere between $25 and $150). In general, jokes and other "punchline" work will command a higher price than poetry or verse. If you are submitting artwork, you will be able to license your work. This gives the company to reproduce your work for a limited period, and potentially in a limited market (depending on how you negotiate). You retain ownership of the work, and can license it to other companies as long as they don't conflict with your existing contracts. Flat fees for licensing can range from $275 to $500.

Summary:
Find companies who look for freelance designers. Get submission guidelines. Create samples that meet the company's guidelines. Keep trying, even when you face rejection. Negotiate payment.