Schluter makes many transition pieces that can work, but you need to be more specific about the actual height difference. A 3/8" gluedown wood will be virtually flush to tile and not need a height transition piece, just something to hide a cut edge. It's all about the planning stages, before anything happens execution wise.

Your installer can even take a piece of wood trim and router out one side as an easy transition.

If planned properly you shouldn't need a transition. A standard ceramic/porcelain tile will butt up perfectly to a 3/8" wood (as pictured). If you are using 1/2" wood it would be wise to use a natural stone like travertine that comes in a versailles/french pattern. (The tiles in these patterns are usually thicker)

If you're actually asking where you should create the transition, pictures would be more helpful. :)
In our new home we couldn't come up with a place to transition the wood with the tile that looked nice and made sense, so we just tiled everything instead. I figure that the majority of the living room floor is going to be covered with furniture and a rug anyway, so no need to have a different flooring there.