I can't seem to find tutorials on stacking 2 tiers. If you know of one, please share.

Do you just sharpen the dowels and make them long enough to go through the cardboard of the 2nd tier? Will it just sink through? I have never done this...Thanks!

Here is an excellent video from Edna. She is a fellow CCer. Hope this helps.
http://www.youtube.com/watch?v=NvaCSW78ybc&feature=related

Thanks for the tutorial, but I'm still not getting it- maybe a bit slow these days....
what if I've done the top layer in fondant and I'm placing it on top of the doweled bottom cake (this is an odd shaped 3D cake) . Do I still drive the sharpened dowel through the fondant and then try to cover it up? Is there another technique for my situation???

Thanks!!

You can use the sps, no need for dowels. There is a sticky in the How To Forum by Leahs with pictures and instructions. I only use this method now for any cakes I do. HTH

I've made lots of 3d cakes without an sps. Without the SPS, go ahead and put the dowel all the way though the cake for stability. To cover the hole in the fondant, color some BC to match and spackle the hole. It works great!

Thanks for the advice - I'm committed to the dowels at this point and it's good to know...