Structural effects: you've seen Lewis dot structures and read about "resonance" sharing of charge in anions like carbonate and sulfate; carbonate is planar trigonal, and resonance sharing of a -2 charge by 3 oxygens can be looked at as a "formal" charge of -2/3 on each oxygen in a nice symmetric triangle, so no dipole; sulfate -2 spread over 4 oxygens arranged tetrahedrally around sulfur --- same argument, same result. The ammonium ion same argument for 4 hydrogens sharing a +1 charge in a tetrahedon. Finally thought of one, thiosulfate, same as sulfate except one oxygen has been swapped for a sulfur atom, gives us a trigonal pyramid, or tetrahedron (not a regular tetrahedron) with the majority of the -2 charge sharing among the 3 oxygens on one face; -2 charge on one face, 0 charge on the opposite apex (the second sulfur) 3, maybe 4 angstrom separation; Houston, we have a dipole.
Neutral molecules: water is shaped like a boomerang with H at either end and O at the elbow; the O attracts the electrons contributed by the hydrogens to bond formation more than do the hydrogens giving a net negative charge on the O, and net positive on both hydrogens. I can't draw a straight line through all three atoms, but I can draw a straight line with the oxygen and net negative charge on one side, and the hydrogens and net positive charge on the other and see that there is a dipole acting perpendicularly to that line. You've noticed by now that I don't use graphics at all --- time for you to digest this and tell me whether it's been properly prepared.