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: 他日泳げるために、毎日練習しています。
The second one is ため in context of causal clauses. For example: 大雪が降ったために、空港が使えなくなりました。 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.