Lowest possible power
When I use the lowest possible power, I always use search and pounce. This means that I only answer to a CQ of other stations. I rapidly switch to the wanted (low) power, before I answer a CQ.
Only when I am certain that my signal is not heard, I will increase my power. When I have to increase my power, I usually make a step of 3 dB or 4 dB.
The S-meter is very important, when I use the lowest possible power. When a received signal is S9 + 10 dB, instead of 599, I reduce my power with 10 dB.