Domination maps in UT were generally built more like Deathmatch maps than any other gametype. Control points could be of a varied number, and were generally just scattered around the map.
Double Domination's mapping has changed significantly. The gametype its maps are closest to now is probably CTF – they are generally symmetrical, with a control point at each end of the map in a base of some sort. However, instead of playerstarts being placed at either end of the map, one base per team, they are placed in the centre area of the map, and not usually seperated by team. Examples: DOM-ScorchedEarth, DOM-Suntemple.
Player Starts should be of an equal distance to control points - especially if they have specific Team Indexes. One team should not spawn closer to control points than the other.
Control points should be of a good distance from each other, usually opposite ends of the map.
Entrances to control point areas should not be choke points - there should usually be more than one way in.
To add a control point, add an actor >> NavigationPoint >> JumpDest >> JumpSpot >> GameObjective >> DominationPoint >> xDomPoint >> xDomPointA/B
One xDomPointA and one xDomPointB should be placed in the map.
Double Domination offers a lot of variety in what maps can be like. Possible examples:
Blue Team and Red Team both have a base with a control point in each (regular CTF style map). In this type of map, you would have to hold off the enemy at their own base for ten seconds to score a point.
King Of The Hill style gameplay - Both control points are next to each other at the centre of the map. Effectively - if you have one control point, you have both - you just have to defend it for the time needed to score.