You won't be able to cut back as much as you wish. Heaths and heathers should be cut back annually each season after they bloom. If you wait too long, they develop an extremely woody interior with new growth only on the outer edges (they also tend to splay open as well, revealing this less than attractive feature). Cutting too far into the wood will not generate new growth and you will have essentially just a mass of woody stems.

As far as tools are concerned, my tool of choice for this task - and scores of other similar pruning/shearing chores also - are sheep shears. Easy to use with one hand (while the other grasps the material to be removed), easy to maintain a very sharp edge and relatively inexpensive.

Here is a link that might be useful: sheep shears

As was said, you won't be able to cut back as far as you'd like. You must retain some greenery or the branch won't grow again.

Beyond that, I use grass clippers to trim mine.

Thank you both for the answers. I had read that you should trim your heathers or they'd get woody and twiggy, but I didn't know they wouldn't get any new growth on the woody parts. Lame! My consolation is that it was that way when I moved in. Oh well.