Hi,
Perhaps I should emphasise that the "series contacts" principle (in #7) is specifically for Inductive loads, which can generate a very large "overswing" voltage as the contacts open, when an arc can burn the contact surfaces (or worse). A capacitor (perhaps with a series resistor) across the contact(s) helps to "tame" the overswing, hopefully lowering the resonant frequency sufficiently that the contacts can be far enough apart when the peak voltage is reached. Similarly a diode (again perhaps with series resistor) across the load will maintain the current flow, thus preventing a high voltage being generated. But beware that the continued current flow may slow (delay) the release of a driven relay. Conversely, short-circuiting a motor can act as a brake (eddy current), or even recover some of the energy (regenerative braking).
For purely resistive loads, connecting contacts in parallel might help (a little), but as hippy has implied it's a matter of "horses for courses". Putting contacts in parallel may help the "running" voltage drop a little, but when the relay opens or closes, one contact will probably move before the other and one will see the full current, just at the point when the contact resistance is at its maximum.
Cheers, Alan.