Can someone advise me as to how and what kind of threshold to use on our doors leading outside to the deck and the door leading to our garage? We are putting down ceramic tile and have no idea how to lay this threshold. The people at HD and Lowes could offer no advice at all. We can't even figure out which direction is best to turn it in (taller side inside or facing out?). It seems like wider side out is better to keep out water. Can someone advise? We are going crazy!

About 6 months ago I tiled my kitchen floor. After pulling up several layers of linoleum, I ended tiling over a the original hardwood floor. Since then several cracks have developed in the tile and and are growing longer through several individuals tiles. The cracks are in different parts of the floor but they are so far they are all parallel. Now the floor I tiled on top of is rock solid. I have a solid subfloor with a solid hardwoord flooring and I installed 1/4 inch of that hardibacker stuff... so it is hard for me to think that my floor is sagging thus causing the cracks. Anyone have any ideas on likely causes and possible remedies?