With permanent setups where the system is housed in an observatory this only needs to be done once, as I use a portable setup I have to go through this routine every time I put the system away. For ease of use I have everything set up on a big set of wheely bars which aids in the set up process.
To get a rough polar alignment I will already have set alt setting on the mount to the correct lattitude setting for where I live which I obtained from my portable GPS system which I use for mountain biking. Then using the digital compass on the GPS I find out where north is and line up the mount so that the RA axis is pointing due north.
Using the adjustable height feet on the wheely bars and a small spirit level I now level the mount as best as I can. Although an unlevel mount can still track, it will always be under less stress and more accurate if properly levelled. This again is something that is best done in daylight and doesn't require anything to be connected to the mains or a computer.