A Carpenter's Trick For Finding The Center 

Yeah, I do this by habit now and it has served me well.

Yeah, simple is usually better!

I use that idea when measuring for crown, especially since it's easier to see the mark or a finish nail than to bend the tape into a corner.

Well, you bring up an important point. Accurate compared to what? Truthfully, it isn't that important for a tape measure to be accurate in most cases, but consistent. In other words, if a tape is consistently off by a 1/16th it doesn't matter unless you end up switching to another tape in the middle of a project or you are working with somebody else who has a different tape. When I work with a partner, we compare tape measurements before we start and then make adjustments if needed. When working alone I try to keep the same tape at my side throughout the project. Inconsistent tapes can be found by taking several measurements of the same item or mark or by looking closely at the end hook for damage. Sometimes the hook gets slightly bent, for example, and it will throw off the measurement depending on which side gets hooked on the workpiece.

Laying out tile in a room requires a balance of circumstance. Finding the exact center of the room is probably not going to be very critical in comparison to the influence of other factors. You could use this method, for example, to find two center points between two walls and then connect those points with a straight line. Perfect, right? Except that the two walls may not be parallel, so now when you get your tile pattern to the wall the grout line will make it obvious. Sometimes it's better to set up the pattern parallel to one wall and recognize that the other wall being out of square will be hidden by a vanity or furniture or whatever. I suggest you take a look at this video on the subject: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-IsJyfUlLzrg.html

You prefer a folding rule?

What to use instead?? I'm in if you know the solution!! :)