Coolant resovoir
 

My car occasionally leaks coolant. The coolant in the resovoir is a hair below the MIN line when the car is at operating temp. Should I put more in, so it's up closer to the MAX line?

I have had the opposite problem. My resovior went over the max line and I started leaking coolant. I am looking for the point of origin for the leak, but I so far cant find it. I would say in your case add a little more coolant. Just dont go past the max line.

In both cases I recommend top up the reservoir to the max line and check every second day. It the level does not stay there, there is a problem.