And he was asked:

What is the meaning of when some scholars say, "this is a weak hadith," or "it is not authentic"? And in an issue, if there are two narrations, or two opinions, then is it permissible for a person to  just follow either of them? Or where should one place his trust?

So he answered:

The scholar may say, "it is not authentic," in other words, this quote is weakly proven (to trace back to the Prophet Sal-Allahu Alayhi wa Sallam), even if some of he scholars have used it as evidence. And a weak hadith is the same as one which has been narrated by someone who is untrustworthy, or who is weak in memory, or for a lack in his justness.

And if there are two opinions to an issue, then the individual may follow the one which appears stronger to him, or he may follow some of the scholars who he relies on to convey to him the most correct of the two opinions.

Sheikh Al-Islam Ibn Taymiyyah

Majmu` Al-Fatawa 18/43