Timing is accomplished by watching the buds on the host tree. When the buds are only just beginning to change from the winter dormant mode to the first bud on the host tree showing only the smallest bit of color it is time to apply the scions you plan to graft. You must watch for bud push/break every day because when it begins it will continue quickly. The scions should be taken without any leaves and stored in a plastic bag in a refrigerator or the coolest spot available like in the shade on the north side of a house. They should be taken in January at the earliest.
More later.