Never cross a ripline without being sensitive as to its effect on the boat. Did it favor or hinder your progress? Particularly in light winds with smooth seas look for a line of drift or scum which marks the interface between two bodies of water moving at different speeds and /or directions. When the wind is up look for a difference in the roughness of the water. Current against the wind causes the water to be rougher. Use it to your advantage.
A long yarn tied to the backstay above your head and extending several feet forward of your steering position is a good telltale for running and you avoid the pain in your neck trying to monitor the windex at the masthead.
Whenever you meet another boat on the opposite tack or jibe, one of you is going the wrong way!
George Hansen, Vela