Lifting the Skyline is necessary for almost any maintenance procedure, and using a jack-lift to do so can be difficult to figure out. Honestly, it took me at least a few hours of mucking about trying to figure it out while making sure I was being safe the first time I did this. There's a big risk in doing something like this, you need to take every precaution necessary to stay safe, always have a buddy with you too.
Some people have managed to completely ruin their cars by improper lifting, trying to jack the car up using the frame rails or worse the floor panels will without doubt, result in a damaged chassis, just don't do it like that. This, is the proper way to do it, safely, with out damaging anything. Note: E-brake should be on.
Step 1, if your car is low - which it probably is - you're going to need to drive your front wheels up onto a set of blocks, just enough so you'll have enough space for the jack to slide under the front bumper.
Next, crawl under the front of the car, and using a work light, find the "X". There's a big X stamped into the base of the front subframe, this is where Nissan has made the most secure lifting point, don't lift from anywhere else, and make sure it's right in the middle. Note: NEVER use a jack on a soft or unstable surface, concrete is the best, and on a hot day, there's enough pressure that if you do this on asphalt you're likely to leave a large dent in the asphalt. Also make sure the surface is flat and level or the jack will move.
Lift the car slowly as high as you need to go, continually watching for stability. Using 2 jack stands, slide each into position inside the front subframe on either side, right where the tension rods connect to, you'll see there are 2 nuts inside there, position the jack stand so as to not hit the nuts. If you cannot manage to do so because your jackstands are too large or something, then just use another point on the subframe, the subframe is the key here. So, like this on either side up front:
With the front end fully supported, slowly lower the jack lift, checking and repositioning your jack stands to accept the weight of the car as necessary. Once free and clear, move to the rear with jack lift.
At the rear, looking under the car locate the rear differential. Just in front of the rear diff, you will see a circular subframe support, the rear drive shaft actually passes right through the center of the hole. This is your rear jacking point, it is solid and will not cause any damage here.
Begin lifting the rear until you have enough height that you can slide 2 jack stands onto the rear subframe to support the weight, I use the triangular metal pieces where the subframe meets the chassis, there is a large bushing and bolt which holds the subframe to the chassis.
Slowly lower the jack allowing the car to come into position on all 4 jack stands now, and remove the jack lift from under the car. Putting the car back on the floor is the exact same but in reverse. Never work on your car with the vehicle weight supported only by jack lift, it's too dangerous and not worth the risk.