My pomeranian Oni is trained to go out and use the box. I can't even begin to describe how wonderful it is for him to have that option. I got him as an older pup (about 9/10 months) and was lucky that he took to it easily. I paper trained him first (it is alot easier to find info on that) and when he was down to using a couple sheets of newspaper, I moved it into the box.
Here is a link to a litterbox training site that I have book marked
http://www.kturby.com/litter/litter.htm
and there's the purina dog litter site:
http://www.doglitter.com/GetPage.asp...8277&T=3953603
the clumping litter can be very hazardous to the dogs health if ingested (such as choking and bowel obstructions)..your much better off using recycled paper type litter, or you can stay with regular newspaper (which is much cheaper).
Oni prefers to go outside when possible, and only uses the box if I am running late comming home, if he is sick, or if the weather outside makes it difficult to go out.
As another post metioned, there are little grass setups you can buy for your dog, which is also great if your dog is already trained to go outside...I might have to try one out myself for my new pup. When training, there will probably be regressions every once in a whice as your pup learns that you want him/her to go in a specific place in the house. Just stick to it and you will probably be okay, although there are a few dogs that just can't figure it out.