Roughly, my textbook taught me two major usages of -ため:
First, in context of a final clause, it is the colloquial equivalent to -ように and marks that the verbal expression connected to ために is the "goal" one tries to achieve through the verbal expression followed by the -ために phrase. Example:
The second one is ため in context of causal clauses. For example:
Especially in this case, except for paying attention to context and the general sense of the sentence, are there any other "hard" criteria by which I can distinguish ため being used in a causal function and ため being used in a final function? For example, when ため was used in a final function, I think the preceding verb was always in present tense. In the case above, the preceding verb is clearly set into past tense.