Some of this information may be redundant with other guides / info on attacking a level-10 NPC, however I just want to share how things went for me.

I had one open city slot to use.

The NPC I attacked was fortunately at a distance of 1.0 mile from my attacking city.

My starting science going into the attack was:
Mtl Cast-10, Info-10, Mil Sci-10, Mil Trad-10, IW-10, Comp-10, HB-10, Arch-10, Med-10 and Mach-7
What each of these do specifically for the attacks I can only guess, just sharing where I was at.

Using a Feasting Hall-10 and a Rally Spot-10, I attacked with 9 heroes keeping the 10th one in as mayor.
The attack values of my heroes in order of the waves sent out were as follows:
138, 133, 130, 125, 122, 122, 109, 108 and 103.

In addition I used a corselet, penicillin and warhorn. I applied an ensigna to my first wave of attackers to boost the amount of attacking units, remembering to unclick the box during my next wave.

With each attack wave I sent a rainbow consisting of 1 of each of the following:
Worker, Scout, Pike, Sword, Cavalry and Catapharact

The starting quantity of units I had was in my city before starting the attack was: 314,739 Archers and 259,529 Warriors.
I may have over done it at the start, but being my first time I wanted to make sure I was ready. Each attack wave took a 1 way time of 2m47s so I tried to space out my attack waves to between 30-40 seconds to maintain constant strikes.

Also, after the first wave of attackers returned I tried as often as I could to heal units in the Rally Spot while still maintaining to send out consistantly timed waves.

I then scouted the city with 1 scout continuously until I found a defender with a level of 5. Here is how I attacked.

1st wave: 113,994 Archers & 11,000 Warriors + rainbow

2nd & 3rd waves: 25,000 Archers & 20,000 Warriors + rainbow

4th and every wave after: 20,000 Archers & 20,000 Warriors + rainbow

The results were:

34 attacks and a time of 24m27s

Losses: 27,767 Archers & 18,314 Warriors (11,000 Warriors were lost on the first attack)

Rewards recieved: 2 Nation Medals and 3 Freedom Medals

So far it has been suggested to me that for the additional waves that I use 35,000 Archers and 5,000 Warrors. Any suggestions on how to decrease troop losses, specifically to the Archers, is appreciated.

Oh, and one more thing, don't forget to address the low loyalty right away in your newly taken city or you might have a riot.