I like what Merlin said about bearing & range.
Actually, making sure of where you will be in a crossing/meeting situation is a simple no-brainer:
1. you're sitting stationary in your cockpit & keeping a steady speed & course. hopefully, the other guy is doing the same.
2. use a stationary vertical object for starting your observation. A stanchion, bimini support whatever.
3. Using this, look at the distance between the stanchion (or object) and the oncoming boat. Now keeping your head in the same position while watching, if the oncoming boat's distance gets closer to the stanchion, the boat should pass in front of you. If the distance increases from the stanchion, you should pass in front of him.
It's that easy. if unsure, try it a few times & it becomes automatic.
However if he's a squirrel, the above does not apply. The rule is for you to keep a steady course so as to communicate your intention to the other boat. If the meeting/crossing looks to be close-quarter, be demonstrative and turn your boat a good 45°(or more) & hold steady for a bit. This communicates to the other boat you're intention evidenced by your changed course. This show of your hull (side/beam) will let him know your intention & where you will be when meeting/crossing in close quarters.
CR