My Family Raised, trained and showed Shetland Sheepdogs. I could help point you towards a reputable breeder if you let me know the area in which you are from.
First and fore most.. you MUST know that a Sheltie WILL bark. They were BRED to be barkers. During the time of the "original" shelties, they were used to herd sheep around on the Shetland Isles of Scotland. High winds and hilly atmosphere made it so that the shephard never had consistant sight of the dog. SO it was bred into them to bark consistantly for the shepherd to hear them at least.
They can be trained not to bark at things, but barking comes insanely natural to this breed. Many people who acquire them, dont realize the amount of barking they can do without proper training of it
Just a heads up
Other then that, Shelties excel at Obedience and Agility work. They thrive to work. They aren't a breed to be happy to relax at your feet if they have had a full day of nothing. They will develop bad habits, just like any herding breed basically, that will cater to their energy needs - whether it be chewing on something they aren't supposed to be, digging etc.
They can be extremely intelligent. I suggest purchasing your dog from a working titled parents. Meaning they have their CD, CDX, UD etc etc titles. If you purcahse a puppy from those type of parents, you can be confident youre sheltie will have a "brain"
If you purchase from strictly a CH titled lineage, you will have either a stubborn sheltie(which they CAN be) or an unknown brain Sheltie just waiting to discover it.
Our Previous shelties, were universally titled. Had their Chs as well as their CD, CDX and were working on UD etc etc. Our stud produced some AMAZING working shelties and some stunning Conformation Champions.
As above, Steve covered all the basics of them as well.
Shelties do have a double coat. They need to be line brushed weekly and regularily brushed DAILY!! Can not stress that enough. The shelties undercoat can matt VERY easily and must be brushed out. Especially behind their ears!!
When you get your puppy - SOCIALIZE SOCIALIZE SOCIALIZE!!
When Shelties are not socialized properly as puppies, they can remain extremely skittish and show "fear aggresion" with strangers etc etc.
Definately give your puppy the benefit of the doubt and expose them to many different scenarios (proper shots pending). Also, make sure you go over your puppies feet daily. Shelties as a breed - HATE their feet touched, so the more you touch them and make it a positive experience - the better!
Our vet was very impressed when she went to touch Crosbies feet and he knew "paw" and he just voluntarily gave her his paw!
Have you decided if you want a male or female yet?