A key force of attraction between molecules is the dipole-dipole force. This occurs for polar molecules as they have a permanent dipole moment. You'll remember that a dipole is defined as two opposite charges separated by a distance. Therefore, a molecule with a dipole has a "positive end" and a "negative end." When two or more such molecules come together, they arrange themselves to maximize the attractive forces (negative near positive) and minimize the repulsive forces (like charges). Dipole-dipole forces can be strong and have a long-range interaction. The distance dependence of a dipole-dipole energy scales as 1/r3. Below is a schematic of an arrangement of a polar liquid. Note that there will always be some repulsive interactions, but in general the molecule will arrange to favor the attractive forces (lower energy).