Now is a great time for you to think about trimming your Boxwood and Taxus. With Boxwood just starting to push out there spring flush of growth trimming the new growth can be trimmed before it hardens off or allowed to flush out to fill in. Either way the trimming done now will be mostly covered up by the foliage that flushes out now. Now is also a good time to go ahead and get an application of fertilizer down. I like to use Espoma’s Holly Tone.
One of the biggest problems I see is from incorrect pruning. Most people tend to trim the sides straight up and down. This allows the top of the plant to shade out the bottom and prevent in from being able to photosynthesize and produce growth. We have all seen (Taxus especially) plants that look like a globe on a stick because of this. When you trim the sides of a hedge or any evergreens for that matter you want to make sure that you trim at a slight angle. This makes sure the bottome of the plant gets enough sun to stay full and healthy.