Len is right that you should not expect the stripes to match at the shoulder seam. Lapels should obviously by symmetrical, ideally with the stripe following the curve of the edge of the lapel and not drifting off the edge. Pocket welts can be made to match if the pockets are straight; some tailors prefer to cut them with the stripe running along the length rather than the vertically. If they are hacking pockets, then the stripes would usually not match, as this would require cutting the length of the pocket on the bias, which could cause the pocket opening to sag with use.
Any horizontal striped in the pattern should match between the body and the sleeve. Ideally vertical seams (such as the front dart and the center back) should fall inbetween stripes so as not to swallow them, although some Italian tailors seem to like to swallow a stripe in the breast dart (there's a thread about that somewhere).
Originally Posted by porcelain monkey
I assume this is because the fabric is cut at a slight angle perhaps to accommodate matching in another area like the darts.
The fabric is never cut at an angle; this would mean cutting on a slight bias which would affect the drape of the coat. The front dart is usually, on striped fabrics at least, kept along the straight so that it runs parallel to the stripes.
The top-collar will usually be matched to the body at center back, it is not always possible to match the collar ends with the lapel stripes.