I started my first air layering last July but failed due to my careless plus less rooted etc. I started again in this April and so far so good, so I am going to cut it from the mother tree in next week and pot it in a 3 gal container.
Please help to tell me what must I do for the whole procedure and not kill the plant with many thanks. 

A photo would help.Size matters in terms of how to handle these.

Absent that,assess root to top growth.
Remove excess top growth/leaf while still associated with tree.
Let it callus and then remove from tree.
If possible place it in a humidity bin for 3-5 days.
Shade and misting as required gradually moving into dappled light.

Hi 
My air layerings I usually separate them from the mother tree and pot them at the end of August.
The 1St one I made  I was so happy it rooted that I separated it end of June What was the rush? Impatience.
The roots were very tender and and thick when iI cutted it to plant I brook most of them taking  the wrapping off .
It died after.Lesson learned.
Now I wait untill the roots are well matured before I cut off. No more accidents and they still get time to accomodate in the pot before going dormant for winter.
Hope it helps.
Rio

I added some dirt on my brother's fig tree last year, it covered many suckers/lower branches as well.  Last week, I checked and all of them rooted, They had weak roots of  1 inch without feeder root, I potted few of them.

Since it had less roots, I removed most of its leaves and kept one leaf and bud tip left, then I cut it and put them in 2 gallon pots with good potting soils and bone meal.
Then, I put them in shaded/cool area, No direct sun, misting it whenever I pass this area, After 1 week, It has grown some new leaves, and roots increased from 1 inch to about 2 inches, I will gradually move them into dappled light next week.

It is easy to take care of small/short branches, They don't need to start with lots of roots, If it is long branch, it needs more roots and more caring.

I started air layering(no scoring) on my fig tree at May, it has roots, not many, I will wait for awhile.

Since root-ball broken off experience , you may do extra step to harden rootball by reducing water to minimum for 1 week, it will harden root-ball and less crisp.

Good luck for your air layering

Hi pacifica,
The root amount is the key. Don't rush because you see one root.
Where is the airlayer ? Near the bottom ? in a higher branch ?
You may want to forbid the branch to grow too much - that is pinch after 3/5 leaves.
Sometimes higher branches can grow a meter /3' and the roots will have a hard time feeding all that.
A picture would help :)
Once separated you want to keep it with a stake and well watered in a shady spot for two weeks, and then slowly bring her to the sun and act if she wilts .
You could remove half of the surface of each leaf of the airlayered part a week before removing it.
Then it is a matter of own preference ... and experimenting .