If your table top has melamine or other plastic laminate on both the top and bottom surfaces it will not move. Figure 8 fasteners are a good choice. There are other products and methods such as "Z" clips, using woodenblocks trimmed into an "L" shape or using the new top attaching bits to rout slots in corner braces so screws can move if need be. Perhaps understanding how the wood moves will help even more. Think of your wood as being a bundle of straws. Moisture can easily pass in and out of the ends with no effect on the length. But the moisture takes up space and can cause the "straws" to move apart or side to side. This cross grain movement is what we try to compensate for when attaching a top or building panels.