IMF

It depends on the species present and the difference in electronegativity. In the case of CH3F fluorine is extremely electronegative in comparison to carbon. It's just something you learn. Elements in the same group as fluorine tend to be very electronegative. If it were just CH4 you wouldn't get this dipole-dipole intersection due to the lack of difference in electronegativity between hydrogen and carbon.

If you have a lone pair on your central atom and hydrogen atoms bonded to it then you will have hydrogen bonding. E.g H2O


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So it's just something that'll 'click' eventually
Thank you!!!