How do I recognize the null and alternative hypotheses in a problem?

[cmab]

I really don't understand hypothesis testing.

How do I recognize which one is Ho and Ha in a problem?
Is there a particular trick to facilitate my lfie?

 

[EnumaElish]

http://en.wikipedia.org/wiki/Hypothesis#Evaluating_hypotheses

Null is the hypo. that you are attempting to falsify through your empirical observations. To falsify the null, you need to "prove" that your observations are not due to pure chance (or the probability with which they could be pure chance is low).

 

[Gokul43201]

http://davidmlane.com/hyperstat/logic_hypothesis.html