Okay guys, throwing personal insults at each other helps no one, so cool it...both of you! Taking the time to post in proper English with at least average spelling is key to establishing credibility. On the other hand, being overly critical of something that is`nt directly topic related, inflames the situation and is often better left unsaid...
As to your question and Mooz`s point, your friend will be far better off getting a lesson. The fact of the matter is that good instructors are taught good communication skills that work effectively. You can be an awesome rider and still not be good at teaching. There`s no shame in that; it is a learned skill. So, having said that, see if you guys can`t get together some change and get him/her into a freestyle lesson with a certified freestyle instructor. It is money well spent and depending upon the instructor and the resort`s policies, you may be able to shadow and pick up some tips on instructing which could help your friend out later when you want to teach him/her something new.
Barring that, without visually seeing your friend ride, it is difficult for anyone online to diagnose and therefore give good tips. In general though, when jibbing any object, keeping your upper body centered over the top of the board is crucial. Any slight shift can create an unstable condition where the board slides out from under you. In any spin, having a bit of rotational force generated makes life easier. Alaric eluded to this regarding positioning of the shoulders. It is often referred to as "pre-winding" and can be an effective tool for generating good spins if not overdone. One good way to do this is to remember to keep the head turned in the direction of the spin. Often, people allow their head to "counter rotate" and this will slow and stop your spin pronto. Also, try to avoid looking down at your feet; this is a very common problem for new jibbers and it totally throws off your entire balance and stability.
As a matter of progression, try to find the biggest (widest) box you can that is an easy ride on feature where he/she can spin with little danger of falling off the side of the box. The key to good snowboarding including jibbing is confidence and confidence only comes through progression and establishing a track record of success.