Order (blue) begins near the Lighthouse objective (blue square on page 1 map) and Destruction begins near the Barracks objective (red square on page 1 map). After the initial objective, both sides have a straight path to the very strategically important Fortress. It should be noted that Order actually has two paths, the lower of which is faster to the Fortress than any route for Destruction. Both sides should be careful to make sure at least one person actually stays and captures the objective near their spawn location. Occasionally everyone is in such a hurry to get to the Fortress that nobody stays and caps. Generally, it is best for a low level ranged DPS to handle this duty since it is actually helpful if they arrive at the Fortress a few seconds later than the massed army.
The first clash generally happens at or near the Fortress. Assuming balanced team composition, there is usually a large melee battle at the flag with ranged DPS trying to take out each other or each other's healers. Occasionally some members of each side will try to climb the walls to get an advantageous position. This works only if the opposing side is not paying attention. Usually it is better to make use of environmental hiding spots and line of sight for defense.
Sometimes one side will send some of their DPS directly into the back ranks of the foe hoping to take out their support. If they can drop a few healers or ranged DPS fast, this can be very effective. But bear in mind time spent away from the flag is time the other side can be capturing the objective.