Actually I liked the first area it was small with just enough hidden areas that I spent a good 2-3 hours just sneaking around tranqing people my first run through it. :)

This thread helps explain what a wonderful job they did on creating this game. Suggestions about stealth, guns, melee, augs, tactics... play how its fun for you and you can't go wrong ;)

But, since you asked about "no killing" I always keep the prod, baton, and tranqs. You can also improve the range on the bow, making it much easier. You only have to hit them ONCE and they will go down (pending which type of enemy, but once is the standard rule of thumb). Take off in the opposite direction so they can't spray you with fire or tranqs of their own and double back after about 15 - 30 seconds. They will be napping then. (however, they can run for help and hit alarms while the tranq is doing its work too... so keep that in mind).