When to look for leaks:
Usually the first sign of a fuel leak is fuel smell through the vents, especially when the engine is cold. The second sign of a fuel leak you don't wanna know so you'd better start looking at the first one...
This usually happens on cold mornings. The metal fuel tubes are contracting and the old rubber hoses are hardened so they can not seal tight.

Where to look:
Basically every rubber fuel hose in the engine bay. More specifically though:

1. Hoses attached to the fuel filter (in the upper right corner of picture 1.) and the fuel return line which goes parallel to the fuel filter line.

2. Fuel pressure regulator hoses. Apart from the hose visible in picture 2 there is a hose going from the pressure regulator down to the fuel rail below the plenum.

3. Fuel dampener hoses (see picture 3.)

4. The hose that interconnects the two injector fuel rails beneath the plenum. It's well hidden under the throttle linkage in the front center of the engine (4.).

How to look:
Remove the top engine cover. Work only on cold engine, otherwise the fuel evaporates to quickly. It should be enough to turn the ignition on and off a couple of times to build up the fuel pressure. The fuel pump is switched on for like 2 seconds to pressurize the system after the ignition is turned on. Sometimes though it's better to start the engine cause it adds some vibrations to the system and thus causing the fuel leak to become worse.
After that you need to use a special tool to localize the leak... your nose :) It never failed me. Look at the metal pipes that the rubber hoses attach to. You will notice them getting wet if there is a leak.
The fuel rail interconnecting hose is a little bit tricky though. Look from the front of the engine between timing belt cover and throttle linkage assembly. You should be able to see the hose in picture 5 (the picture is taken with the plenum off)..

How to fix:
First approach is to try to tighten the clamps. Tighten and recheck.
Unfortunately this may not cure the problem. If you absolutely must apply a temporary fix you can try one more thing. You have to loosen the clamp and move it a bit to the side. In this way you can clamp on the thicker part of the hose an thereby apply more pressure from the clamp.
WARNING! Release fuel pressure at this time (see below).
Tighten and recheck. Be prepared that new leaks may appear in the future!

The best thing of course is to replace the old hoses and clamps. Use only high pressure fuel hoses! It's best to use the original Nissan fuel hose since it's thinner then the ones found in ordinary stores. Have some rags handy cause even if released the fuel pressure, there is still fuel in the system.

Fuel rail interconnecting hose fix:
The hose is really hard to get to with the plenum on. In my case it was the right end of the hose that was leaking.
Since the clamps on it are facing up, you can not reach them easily with a screw driver. I managed to loosen the clamp from the 
top, through the linkage assembly.
Turn the clamp to face it to the front of the engine (pic 5.). You can now easily reach it with a screw driver going between timing belt cover and linkage assembly. Tighten it and recheck for leaks.
Now this is a very TEMPORARY fix. Make sure you replace the hose next time the plenum is taken off the engine. 
I would recommend fitting two clamps on each end of the hose at the time.

Releasing fuel pressure:
First you have to disconnect the fuel pump (or the fuel pump relay). To get to the fuel pump connector, remove the spare tire and remove the cover below it. At that point you will see the top of the tank and the fuel pump connector. Disconnect it. Now start the engine. After a short while it will die. Crank the engine a couple of times to release some more fuel. After that there is still a little pressure in the fuel system so have some rags handy to catch it when undoing the hose.

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