A trick is to use a switch, say in your 5 volt line.
Close the switch and power your circuit, It operates noramlly.
Place your current meter leads across the switch. One on each side.
Current reads zero. Open the switch and now the current will flow through your meter and give you a reading.
This is especially convenient for measuring the very low current that is drawn when a system is set to sleep - changing the meter range coukd be disruptive, the switch provides a way of inserting the meter into the flow without changing anything else.
Thanks everyone for your answers, really helped me. I bought a usb dongle and can easily see my currents and voltages.
Now some more questions.
A) Your answers about the libraries really answered my questions but where can i find deeper knowledge about the inner workings of the arduino compiler? For academic purposes.
B) I'm finding it really difficult to grasp the concept in depth, of cable impentance, noise and voltage refs and their significance in analog readings. I mean i get that they play a significant role but it seems to me like black magic. Where can i find something to read about those things, but for dummies? Google it, is not acceptable, nor wiki.
C) How do you guys create ur THT pcbs? I mean how do you solder components that "far away"? I tried single core cat6 cables but they are melting. Tmrow i will try silicone 0.15 cables but im thinking about coil wire. Also by continuing the b question, what are some good practices? Common grounds? One side of pcb for signals, the other for +5/gnd? Overlapping cables etc?
Anyway i will keep this thread for future general questions i might have. Thanks everyone so far for their help!
I'll give it a try though why not.