The most important areas to measure are around the neck, around the largest part of the chest, and the distance from the neck to the waist. The sweater’s length should end around the waist, leaving the lower bellow free. Knowing your dog’s actual weight will also help you to determine the correct size. If possible, take your dog along to the store with you try the clothes before buying them, as returns are very difficult when it comes to clothing for animals.
It almost goes without saying, but we will mention it anyway, dogs cannot, or should not, wear pants — only sweaters and jackets.
Check especially around the arms (in the "armpit" area) and around the neck to be sure there is freedom of movement, but not too much excess fabric. Also, choose pieces that are easy to put on and take off, nothing you have to pull too tightly over your dog’s head or that cause you or the dog to struggle.
Another important consideration is checking for any additional parts — like zippers, hooks, buttons or tags. The best pieces will have nothing that can be chewed off and swallowed. Some outside jackets are made with hooks to attach a leash to, but they are meant to be worn only under direct supervision and should be removed once the dog is left to her own devices. That is, when you are not directly observing her, such as during sleep/work/other hours.
This may also be the prefect time to take up knitting or crocheting, or to ask Aunt Suzie for an extra gift of her time and talent. And believe us when we tell you that dogs really do not care about the color or style you dress him in either, so go ahead and get (or make) the matching owner-pet-sweater-combos. Your dog will love the attention you show him while putting the clothes on, so just have fun while you stay warm!
Image source: Emery_Way / via Flickr