Cutting yew hedges is a very satisfying Summer job. Like most evergreen hedges, yew is best pruned during the growing season. It carves easily into clean geometric shapes, especially when using a nice sharp hedge trimmer. I would advise anyone thinking of investing in a hedge trimmer to get the longest blade they can afford. Larger machines do obviously cost and weigh more, so require extra muscle power and cash. But if you've a lot of hedges and are concerned about the finish, then you'll be rewarded with a much more even cut and longer reach.
Unlike most other conifers, Yew will reshoot if cut back into older wood to achieve the desired shape. They're quite slow-growing, so heavily-renovated specimens can take several seasons to fill out again. You also need to be careful with the prunings as they're quite toxic, especially to livestock. Yews' poisonous compound, Taxin, is used for making the chemotherapy drug Taxol.
Now's also the best time to start pruning those members of the Prunus family you've been itching to take the loppers to. This includes fruit trees like plum, cherry, damson, and peach - in fact any fruit that has a stone - as well as hedges like Cherry and Portuguese Laurel (Prunus laurocerasus & P.Lusitanica). Most of these plants are highly susceptible to a fungal infection called silver leaf, whose spores are active during the cooler months - another good reason for pruning them in the Summer.
When cutting a laurel hedge it's often better to use a pair of hand shears - this makes for a tidier, cleaner cut. Hedge trimmers aren't suited to cutting larger leaves, so tend to shred and tear laurel hedges.
while you're in the pruning mood, be sure to cut back Philadelphus and Weigela,
along with other shrubs that have finished flowering and need to grow fresh
wood to flower on next year. There's plenty to do out there, so don't let me
keep you. Go on, hop to it!