I almost don't know where to start so here goes.
First of all the quick answer would be to visit these guys! - Digital Colour Services
These are the people I use and I think they are fantastic. They suit me, as I can just upload work and they print and post it. And they can do samples. Other people might prefer to go into a local printers and speak to a human but I like to hide behind my screen. They also do a range of prices so it is cheaper the more you get printed.
There is also Redbubble.com. I have an account there but I'm not going to share it here as it needs some updating! You can upload your work and people can buy it directly, so you have no outlay. But you will have to direct customers there and it is an expensive way to buy the cards to sell on in person. I believe they also do prints, though I haven't gone down that avenue.
As for prints, I had a lot of questions myself when starting out, and I think I have become more comfortable with the answers recently. However it is a personal choice and I think you have to make a decision and stick to it. And the decision is probably different for photographers and other types of artist.
Now there are prints and there are prints! We are not talking lino or woodblock or any type of print like that, here I am considering the 'giclee'!
In the early days I would sell a painting for a minimal amount and that would be it, my little 'baby' gone forever, with maybe a rubbish photo (Uni tutors advice of "document, document everything!" ringing in my ears). Unsatisfied with the small amount I was able to get for my original picture I put prices up but they wouldn't sell at these new ridiculous prices. (Prices that more truly reflected the time, effort and experience put into them but too high nonetheless.)
I then moved to working in silk for speed of production, as my paintings had become very simplified the images also suited the style of silk painting that I used. I sold a piece at an anonymous charity auction for £25. I was chuffed, someone liked the piece enough to pay £25 when they didn't know the artist. Okay this didn't seem much, but I was starting to work out how things worked. Of course fewer people can warrant spending hundreds on a piece of work, many more people can spend £60 and many more still £25! But to sell a one off for £25 was not enough for me. One picture is one concept, while I am sure I have many more in my brain, I can't make pieces like I am a production line. So I started to make my silk pieces as editions. Although marked as editions they weren't prints in the traditional sense. Each one was hand painted, but I was using the same image so it seemed unfair to suggest each one was individual. I started with editions of 10, but I still wasn't getting what I needed financially so I raised the edition number to 50. The customer pays the same, I get more for each edition. This was okay although there was a bit of confusion over me charging more for the editions of 10 than the edition of 50 as they looked essentially the same.
Quite a few of my editions of 50 have not actually been completed yet as I started to realise I didn't really want to make 50 of each piece. And with a bit more understanding of printing now I have made the decision to go back to one off silk pieces (also they were getting larger and more detailed.) But this time, have them photographed professionally and printed as posters and limited edition giclee prints (A particular type of inkjet printing with archival quality inks). I can then have cards made up too at a later date should I wish to.
Most printers like large files of around 5MB and 300dpi. Although you could get away with smaller files if only having cards printed.
I asked a local photographer to take pictures of my work - Thank you to David Jones of Artwork Unlimited, in Ashford, Kent for photographing some of my recent work. If you are confident with a camera and have one good enough to give you images to work with that are 300dpi and around 5MB then you can take these yourself. It struck me the other day that it is probably possible to take photos on an old analogue SLR camera and have the film scanned onto cd, or scan the negatives with a special machine onto an sd card and use those images to send to the printers.
Many people have advised me to be careful about printing my work on various items as it might devalue the print. I have come to the conclusion that it doesn't and is actually better to get your image seen as much as possible by as many people as possible. I think what you do have to be careful of is what you are calling a collectable piece of art.
The original should be the most valuable and expensive piece, followed by the giclee prints. You can decide to have unlimited or numbered prints by just signing and numbering, starting from number one. But I decided that to give them a stronger collectable value they should be signed limited editions. I have settled on edition sizes of 250 A3 and 250 A4. Reasonably large edition sizes but this gives me the option to reduce the edition sizes and raise the prices in the future. Buyers need to be made aware of exactly how limited their print is when they buy it. And the printers I use allow me to print one at a time if I wish so they can go straight out to the customer and not be hanging around my studio getting damaged or dusty.
I did not like the idea that when these limited editions are sold out that the image is no longer available for people to purchase. So that is why I wanted to also have posters and cards printed too. These are for people who have fallen in love with the image and want a cheap way of putting it on their wall or sending to a friend, but it is not of archival quality and I also leave them unsigned. I do not want people to think these are works of art. They are not, they are quite clearly posters, mini prints or printed cards. I am also experimenting with using the images on other items. These are also not works of art. This is just the same as what you might find at the Tate Modern or portrait Gallery if you go into their gift shop, paintings printed onto a range of gifts.
I hope this explains about my philosophy behind my giclee prints and cards. Please do write any comments and questions, especially if I have missed anything out.
Please view my work in my etsy shop.