bullroarer:
Hello, I have a question about the Arduino's current usage. I want to play around with some sleep modes to save power from a Li-ion, single cell battery. Before I go sticking multimeter leads in places that I should not, where is the best place to measure current in the Arduino when connected USB? I haven't connected the battery yet, and currently my friend has it on him. A simple 'red lead to +5V and the other to pin so and so' would be good enough for me. Thanks in advance for checking this.
You can't really do it when it's connected to USB. The current measuring device has to go in series with the power supply.
https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter/measuring-current