Heroes are a very important aspect of this game.  The higher the ability of the hero, the better they will be in that part of the game.  Heroes have the stats of Politics, Attack, and Intelligence.  Each of these stats play a crucial role in this game and will greatly help speeding up production, training, and technologies.  I'll first explain the three stats a bit more in detail.

Politics

This stat essentially runs your town.  The higher the politics stat of a hero, the faster buildings build (or demolish), the faster fortified units will be created and the more resources you will receive from your resource fields.

Attack

This stat essentially runs the whole military aspect of the game.  The higher the attack, the less troops you will lose in combat and the faster new troops will be trained.  At certain levels, the build time of troops will reach zero (instant troops).  The higher the attack hero while defending will give you a much better advantage against attacks also.

Intelligence

This stat is a bit confusing with a lot of rumors running around.  The main point of this stat is to speed up the time needed to research technologies in the academy.  There are a lot of rumors kicking around about medal farming and all that, I'm going to stay away from them as none of those rumors have been proven.

Now that the basics about the heroes have been explained, I will now go into hero recruitment.  First to be explained is the base stat.  A rough estimate of the base stat is the stat minus the hero level.  I say rough estimate because you will not know the true base stat until you redistribute the stats on the hero.  In order to redistribute, you will need a holy water.  Level 1-9 requires 1 holy water, 10-19 requires 2 and so on.  Due to the stats being randomly distributed and the higher the level requires more holy waters, it is more desirable to keep the inn at level 1.  A level 1 inn will yield heroes below level 7.  You will want to aim for a hero with a base of atleast 67, 69 is ideal.  Sometimes you will get lucky and find a hero with a base of 70 and above but don't hold your breath on that one as that's extremely rare.

Each town should have it's own dedicated politics hero assigned to it (seems pretty self explanatory but figured I'd point it out).  If wanted to (and what I do), you can concentrate first on one attack hero and one intelligence hero.  If you have multiple towns, you can send the hero between them to gain the higher stat advantage in all the towns.  The easiest way with this is to send the hero between the towns with 1 scout.