You must be careful when laying tile directly to concrete.
If there are any cracks or control joints in the area you are tiling, you'll need to use an isolation membrane--which prevents those cracks from transfering up into your tile over time. There are several types which usually don't add much to the overall thickness of the floor.
If you have laminate directly over the slab, you shouldn't have a transition issue with most floor tiles. The ready-made laminate "T" transitions should work fine.
Christopher Wright, CR - WrightWorks, LLC - Named to the 2010 REMODELING Big50
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