Almost all fruit trees (apart from maidens) will try to bear fruit in the year they are planted and it is really tempting to let them do so. No need to list the reasons as they only make following this advice more difficult....don't.
Instead, please do the following:
1. In the year after planting, by all means let your fruit tree flower if it wants to, but as soon as the blossom has passed, pick ALL the tiny fruitlets on the end of the flower stalks off. Growing and ripening fruit requires tremendous effort on the part of the tree and your fruit tree is young and has not yet established. Let it take the whole of its first year of growth to do just that and to build up a rootstructure than can support fruiting.
2. In the following year, let it flower and then THIN the fruitlets so that no more than half remain. We recommend taking off at least 2 out of three and 3 out of 4 is even better. Provided the branches do not start bending as the fruit ripens you can let these stay on the tree until they are ready to pick.
3. In the third year just thin your crop to stop branches breaking under the weight of the fruit. Reduce fruitlet numbers by about a third and watch for signs of overloading.
4. In the fourth year there is no need to thin except to stop breaking branches. This will be an ongoing risk with the huge croppers such as Victoria plums, Howgate Wonder apples and Comice pears.