There are qutie a few books you can purchase with very sweet doggie sweaters in them. The ones I have aren't that expensive, but they have some very cute sweaters. I have a book called PuppyKnits which has tons of sweaters and even a hat! for your doggie. Since dogs do vary in size and shape, I highly recommend you try it on your dog frequently and make adjustments as needed. I alway use a life line to indicate the last place where it fit the dog perfectly, before I knit on to areas where I may need to make adjustments. That way I can easily frog back to the point where the sweater fit perfectly without any headaches. I also note the lifeline point on the pattern I'm using so I know exactly what I did last.
Not all dogs like or are comfortable in sweaters or outfits. One of my dogs is always hot and prefers to be out in the cold.. if I put a sweater on him he just overheats...even if it is a very light cotton sweater. My other dog loves wearing his sweaters since he's usually cold. So keep that in mind as you're making clothes for your pet. Watch them to make sure they are comfortable, that the 'arm holes' aren't interfering with their ability to walk or lay down.
I really want to make this Knitted Dog Sweater http://michaels.com/art/online/proje...&categoryid=32
, but my husband has put his foot down and said he will NOT allow our boy dogs to wear this girlie sweater! lol