Here is the single most important thing you should do before buying any type of small dog clothes.
MEASURE YOUR DOG!
It’s so important that you purchase something that fits properly. Think of how you buy clothes for yourself, you don’t buy them if they are way too big or sooo small that you have to squeeze into them.
There is nothing worse than being uncomfortable and having restricted movement especially when it comes to your small dog.
Make sure that their legs are not restricted in any way, you want them to be able to reach full stride if they break into a run. So don’t purchase something that is really tight and has no give around their legs.
Here is a link to a great little site that has a sizing chart for your dog. Give it a quick read and measure your pet.
I really dislike buying something and then having to return it and deal with sending it back, getting credited and then starting all over again. It’s easier to just get it right the first time out.