Sometimes it's written in: يُستعمل - where the first ḍamma lets you know that it's passive. It's done that way in cases where there would be ambiguity. Sometimes it's obvious: يقال vs. يقول.
Otherwise, you can usually get used to being able to tell the passive forms just from the context of the sentence. Sometimes I start reading a sentence, get half way through and then realize it was a passive verb initially.
I agree with clevermizo.
In addition to that, usually the first word after the verb would tell you if the verb was passive or active. Is that word the doer of the verb or the receiver, of course you have to understand the context and meaning, if it's the doer (subject), then that verb is in the active voice, if not then it's in the passive. Furthermore, if the verb is followed directly by a preposition, it's most likely in the passive. If a verb on the other hand is followed by a enclitic pronoun, it's most likely active.
Of course these are some observations, and usually in a simple news article, the text shouldn't be as complex.
Literary texts which jumble the word order, or nearly never use a single word for the subject and object in the same sentence or consecutively, you have to rely on the context if the text is not vocalized.