Select Your Best Artwork
Take the Best Possible Photo of Your Artwork
The photo must be sharp (completely in focus), the colors must be accurate (taking the photo under natural light is the easiest), and the shape of the painting not distorted (stand the painting up straight, align the camera with it, don't take the photo at an angle). Eliminate visual debris behind the painting by placing a sheet of plain paper behind and underneath it (curve a large single piece so you don't get a line in the background).
Set the camera on its maximum resolution, to get the biggest possible file. Be sure to get the whole painting in the shot, with minimal space around it to crop off. That said, if you don't have any photo editing software at all (list of free editors), take a photo of a detail or section of the painting rather than the whole thing. Then you don't have to crop the photo before using it for a card.
There is no shortage of options when it comes to choosing a printshop. You can either upload photos online or take your photos into a physical shop. Shop around first. Look at what the minimum quantities for printing are, the weight of card being used, if it includes envelopes or polybags, any hidden costs (sales tax or VAT for instance), delivery charges. How long will they take to print and deliver the cards? If doing it online, is there a physical street address and contact phone number? What is the company's policy on refunds, order errors?
Check if you can use multiple photos in one print order. Can you add a logo or thumbnail of a photo on the back together with some details such as the name of painting, your name, and website. Can you get printed proofs (usually at an extra cost, sometimes this cost is then deducted if you make a full order)? Will the printer add their own name onto the card? It's usually small, at the bottom on the back, but it is free advertising for them and some will take it off if requested.
The affiliates links (Buy Direct) on this page are for a company called Moo.com, which operates in various countries. I use them for some of my own cards because you can print a single order of 25 cards with up to 25 different images. I find it useful for printing small quantities of cards as, say, five different photos gives me five cards of each painting.