If you are serious about grafting then you must get involved with your local grafting communities or meet-ups due to importance of acquiring newly cultivated fruit.
The California Rare Fruit Growers or CFRG is my local group of exotic fruit tree enthusiasts. You’ll meet like-minded experts who teach you everything you need to know about grafting including hosting events at their personalized gardens, special projects, grafting presentations, and best of all grafting exchanges!
https://trianglefruitandnutgrowers.weebly.com/scion-exchange.html
http://groups.google.com/group/fruitnuts
Typically, this is how a grafting exchange works, you show up to an event usually held in the spring time. It’s basically, a room full of tables with bundles of scion wood everywhere in order by type of fruit. There are dozens of excited grafters looking a chance to get their missing variety. The order for taking the scion is either my membership or payment and then the leftovers are the freebies for everyone else.
Be careful of the varieties that are patented! You could get into a lot of trouble grafting scion wood that may be protected by intellectual property laws as some trees take a lot of research and development to produce particular characteristics (low chill hours, no seeds, disease resistance, sweetness, etc).
What I do after a grafting exchange is:
Label the scion wood and put the sticks into a bottle or vase with the bottom- exposed portion in water.
Then I eyeball the scion wood and see which scion wood would will best fit my tree in length, width, diameter and cut the leaves off of it with my pruning shears I also brought with me.
I immediately wrap the scion wood with parafilm I know I will use based on best fit, since I know these have a high probability of success or based on scarcity, maybe this particular variety is hard to obtain. The purpose is to preserve the wood. Obviously, the most successful scion wood to take are the freshest.
Finally, I bundle the scion wood I am not immediately using with a newspaper and place into the refrigerator (temporary) or freezer (longer term).