Polar covalent bonds are covalent bonds in which the electrons are unequally shared, like in HCl.
A pair of equal and opposite charges separated in space such as in the H-Cl molecule is called a dipole.
Polar molecules are molecules that have a net dipole.
Diatomic molecules that have a polar covalent bond are polar molecules. However in polyatomic atoms, this is not necessarily the case as two or more dipoles can cancel eachother out. The shape of the molecule determines whether dipoles cancel out or add up to give a net dipole.
To determine whether a covalent bond is polar, you must check whether one of the atoms in the bond has a strong electronegativity (power to attract atoms), thus creating a dipole. Then check the shape of the molecule to see whether its polar or not (ie if the polar covalent bonds cancel eachother out).
(Electronegativity increases from left to right across the periodic table, and decreases top to bottom.)
ie polar bonds in water and ammonia combine to create a net dipole, making them polar molecules.
boron trifuloride and methane both have polar bonds, but they cancel out with each other (due to their uniform shape) which makes them non-polar molecules.
Hope this vaguely helped.. (its a copypaste from my chem notes). At the very least I'd advise just trying to remember a few of the more common examples, ie water, ammonia, methane. Hopefully someone else can help you out, I'm not the best at chem =)
