Check out the options on the 'Gameplay' section of the options screen. You'll be interested in these options:
* Recruiting: You can increase or decrease the speed of recruiting here. Remember, if you increase the recruiting speed, that will also let the AI recruit faster. In this mode, you need to make sure you bring more than enough units to a siege, because otherwise the AI will have recovered by the time you bring in reserves.
* Food Production: Like the description says, increasing food production changes the emphasis toward sieges and assaults, and reduces the emphasis on managing your empire's supply and blockading your enemies supply lines.
* Resupply Behaviour: Late in development, we added the ability to change resupply behaviour so units don't take food from a city until they leave the supply radius, as opposed to the default, which is to take food as soon as a unit leaves a city. Changing this behaviour means your troops won't starve a city when you're only taking units outside to defend the city. We generally prefer the non-default mode, and the only reason we didn't make it default is because it happened to late in development to update the manual and tutorials.