Where do you draw the line in such a way that other may know for sure the difference?
Sure. This is a commonly misunderstood thing.
Calvinists believe that God has decreed everything that comes to past but that He uses secondary causes. Man acts on his own will, yet man may mean something for evil but God means it for good, such as with Joseph.
Man is still responsible before God. Also we are not told the secret will of God therefore we must act only on His revealed will. with the gospel that means we must offer the gospel to all men.
In cases like this it means we must do what is right and leave the results to God.
A true calvinist realizes that results are God's so we should just be faithful to His command.
If arminianism were true, it could tempt some, like apparently caner to embellish his testimony in order to win more souls. But it is better to obey than sacrifice.
Now onto fatalism and hypercalvinism, that is when people see God's sovereignty as an excuse to do nothing. Like God has decreed when I will die so I can drive wrecklessly and drink while I do....that is fatalism.
Calvinism is ''duty is ours, consequenses are God's'' to quotw Thomas Jackson.
For one, it is our strength to press on, for the other it is an excuse to do nothing.
I hope that helps you out. If you like I can send you some links to even better explanations.