Inspect the reaction to identify the ions or molecules containing the element that is reduced (its oxidation state is less on the right than on the left).

Locate a half-reaction containing both of these molecules or ions.  They will appear on the same sides in the half-reaction as they are in the net reaction.
Click on the button in the red column next to this reaction.

Inspect the reaction to identify the ions or molecules containing the element that is oxidized (its oxidation state is greater on the right than on the left).

Locate a half-reaction containing both of these molecules or ions.  They will appear on the opposite sides in the half-reaction as they are in the net reaction.
Click on the button in the ox column next to this reaction.

Reverse the Oxidation half-reaction.
Determine mutipliers for the half-reactions so they will add up to the Net Reaction and cancel out electrons.
The number of electrons cancelled is N for the Net Reaction.
 

To calculate the E^oof the Net Reaction:

Do NOT multiply the E^o's for the half-reactions by ANYTHING!

Either
subtract the E^o for the oxidation from the E^o for the reduction
or
change the sign on the E^o for the oxidation and add the two.