Answer:
Where the greatest electron density is. And isn’t. Look at water. H-O-H.
The oxygen has more electrons, AND 2 lone pairs - the Hydrogens will be partially positive, and so such a way shows the polarity; am arrow with +-> on the Hydrogen area. The “point” will have a negative sign; usually these are drawn as “partially positive” & “partially negative”, but I can’t draw that. Sorry.
Explanation: