You guys all sound like real pros. So maybe you can give me an advice about CIV V and also you are free to call me a noob, I probably deserve it. Anyway I have hundred of hours played in the game but what ALWAYS has been a problem and I mean ALWAYS is military. I have no trouble defending my own cities and repelling invaders when they come but when I want to attack another civ I always lose. I get catapults or similar (depending on the era) and ranged units for distant attacks and then some horseman or swordsman (or similar depending on era - again) but it never seems enough. I kept wondering what the hell do I do wrong. Diplomatic victory or cultural is never an issue but for once I would like to try and go for domination OR at least capture and destroy one civilization. When I start building too much military my people get unhappy and it all goes to hell. Any tips?
AIs tend to rush for your cities with all their military during wars, so from my experience the best strategy usually is to start off defensively, having them attack your units and cities in good positions, where your units can get support from the cities near your borders to attack the enemies. Then, when there are few enemy units left, move forward and take their cities.
Happiness can be solved by trading luxuries, getting luxuries by allying city states (I rarely do that much), some policies, building colosseums etc., later especially the order ideology can grant a lot of happiness as well. Some religion bonuses can also grant some happiness. In really bad situations you can also try to work other tiles so you focus more on production instead of growth, if cities grow too big you get unhappiness and then they stop growing anyway.