Nowadays PDF is more widely used, but the original problems described below still exist: pdfcrop sometimes does not produce the correct bounding box. This program can be used together with pdfcrop in order to produce reliable bounding boxes for PDF files, too.
Other programs like ps2epsi do not calculate the bounding box always correctly (because the values are put on the postscript stack which may get corrupted by bad postscript code) or rounded it off so that clipping the EPS cut off some part of the image. ps2eps uses a double precision resolution of 144 dpi and appropriate rounding to get a proper bounding box. The internal bbox device of ghostscript generates different values (sometimes even incorrect), so using the provided bbox should be more robust. However, because normal clipping has only a resolution of 1/72dpi (postscript point), the clipping process may still erase parts of your EPS image. In this case please use the -l option to add an additional point of white space around the tight bounding box.