Well, take note of what the gauges do when you cycle the key. Most will zero themselves out.
The volts, oil pressure, tach and water temp (when car is cold) will all return to zero if you cycle the key.
SO what i usually do is leave the front plastic lens off and pplug the cluster in. I also leave the needles off. To take the needles off, lay a thick peice of paper on the gauges (to prevent scratches) and use a fork to leverage them up.
Anyway, with the needles off, you can cycle the key to zero out the gauges i mentioned and then place the needles on (but don't press them on tight) Then move them slightly and cycle the key again and they should zero again. Adjust if necessary until you have it right.
For the fuel, i usually fill the tank before the install and then put the needle on full after cycling the key.
Speedo is a little tricky. take the speedo stop pin out and note where the needle falls. It SHOULD point to that little white tick mark below the 0MPH mark.