Nen Ability

Nen Ability Nen's Nature
Each person is capable of master only one type of Nen ability, this is destined at birth, so if you are not happy with the type of Nen ability you have, it's impossible to change or switch to another one (with the exception of Kurapica, please read on for more info).
How to test your Nen ability?
In order to tell what type of Nen ability you possess, you need a glass of water and a piece of leaf.
Put the leaf inside the water and then hold your hands around the glass, not touching it, then release your Nen ability or power (don't try this at home ^_~). 
If you've mastered the basis of the Nen skills, below are some of the possible happenings:

1. The water will spill out of the cup, this means your Nen ability is Strength (Fellow Nen users: Gon)
2. The water's chemical content changes (eg, the taste changes), this means your Nen ability is Transformation (Fellow Nen users: Killua)
3. The water's shape changes (eg, it becomes a solid), this means your Nen ability is Materialization (Fellow Nen users: Kurapica)
4. The leaf inside the glass floats, this means your Nen ability is Manipulation (Fellow Nen users: Zushi)
5. Some other phenomenon occurs, this might indicate you have a special Nen ability that is unique or is rare among others.

Access your Nen ability using your personality
This is the great Hisoka's way of identifying different person's (rivals and friends) Nen ability.  It's almost always accurate, but since most lack the special skills Hisoka possess, it is more wise to use the glass x leaf x water method indicated above.

• Naive, single-minded - Strength
• Unpredictable nature. Loves to fabricate lies - Transformation
• Highly sensitive person, with a rich imagination - Materialization
• Has a liking for lecturing others, very stubborn - Manipulation

Is it possible to master more than one Nen ability?
Technically, it is impossible to possess more than one Nen ability.  But Kurapica was able to achieve this since he's from a special tribe and also since he made an oath that binds him from using his other Nen abilities on anyone but the Ryodan members.  Kurapica must also turn his eyes to the red color when he's using other Nen abilities, he has trained himself to do this when needed.