When you examine the properties dialog you see them listed nicely but when you just look at a beam there isn't anything obvious to tell you which end is which. Even if you understand which end comes first you probably won't remember how you placed the beam later when you want to change it.
I recall someone telling me that they have everyone sketch left to right and top to bottom so that the Start Level offset is always at the left and top of a beams. Good luck with that! 8-).
If you select a beam however the offset parameters are displayed and if you place your cursor over the offset value you'll get a nice useful tool tip!
For you VIDEO minded folks here's one.