Absolutely, there are clues that indicate the presence of a conclusion. First, it is important to differentiate arguments from facts.
A fact might be presented like this: The population of sparrows in my neighborhood has grown 200% in the last year. This is a simple factual statement that is not meant to be disputed, unless the passage gives us reason to do so.
Conclusion: Therefore, the cats in my neighborhood have been very lazy. Do you see how this is different? My conclusion is based on this fact, but it is certainly possible for someone else to draw a different conclusion from the same fact. The conclusion is a possibly subjective statement that can be argued against.
The conclusion, if isolated, will require support. It will leave you thinking, "Ok, how do we know this?"
There are a number of key words that indicate a conclusion. I used "therefore," in my example, but some other options are "because of this," "based on this evidence," "this means," or "so."
However, the conclusion is not necessarily placed at the end of the passage. If it is at the beginning, then it will be followed by the necessary support. It might be followed by a phrase like "this is shown by..." or "as indicated by..."