5 years ago prior to owning my yorkie & maltese I had no clue and most of all just really fearful I might do the wrong thing or mess up their hair or look. Well let me tell you it is so much easier once you start and a dog's hair is 10x more forgiving than say cutting human hair. You really don't have to be exact or perfect and even if you don't cut even, you will see that a yorkie's or maltese hair will grow out and somehow looks even after a week or so.. don't fret or freak out if right after it doesn't look 100% perfect.
And don't let the groomers scare you like I did when they told me things like:
"oh ppl shouldn't attempt to cut their dogs hair because their hair is different than ours and leave it to the professional". Trust me it's all bunch of lies so we can spend our $$$ with groomers. Well one thing they got right, their hair is much easier than our hair. If you make a mistake or don't do it right on a human haircut it will show up more drastically and there's no way to fix it. With a dog, I've noticed that it will grown out the same whether I cut it perfectly or not so much.
And the best thing is I can do it anytime, a quick light trim or heavy cut during the summer. And the more you do it, the easier it will be and did it mention fun? I honestly feel like a pro. Here are some pics to prove it:
http://img213.imageshack.us/img213/7277/no006.th.jpg