You can prune your deciduous fruit trees up to three or more times throughout the year, but the major cutback should be done in the cold winter months, before the sap rises. Start the pruning season with the early fruiters, such as apricot, nectarine, plum and peach, then come apples and pears. The really late fruiters such as quince and pomegranate can be done last.
Stone fruit trees should be pruned after fruiting but while still in active growth as these varieties are susceptible to a bacterial disease called gummosis. Pruning in warmer weather will allow the pruning wound to heal more quickly and reduce the risk of the bacteria entering.
For citrus you prune after fruiting and before the first frosts. Citrus tend to have a growth spurt after a prune and new shoots will be susceptible. You can open up the tree and take out damaged or diseased branches during the warmer months, just remember this is when the tree is setting fruit, so cut back carefully.