Having the right guns and ammo in the right places will make or break a map. This article discussion best practices for weapon and ammo spawn placement.
In Goldeneye 007, there are six levels of spawns, with three patterns based on the loadout. Maps had as few as six spawns (basement). Goldeneye Source can support up to 16 players, so the original system has been expanded upon to accommodate the increased player count. There are now 8 levels of spawns with 1 typically being the weakest weapon and 8 the most powerful.
Your first concern are the Level 8 spawns. You should always have two Level 8 spawns. The 'best' weapon on the map spawns on 8's, so you want to ensure that there are two places to find it. Keep them spaced apart, and consider how team play is affected by them. If one side has better access to the 8's than the other, it's not bad, since teams switch domains every round, but it does mean your map will be an attacker/defender map in team, instead of a neutral battlefield. Choose the style that suits your map. Facility is naturally an attacker/defender sort of map because of the chokepoint. Complex is certainly a balanced battlefield layout. Additionally, in Man with the Golden Gun, the Golden Gun will choose a home randomly from Level 8 spawns and spawns marked as Golden Gun-friendly. Use this to control how much variation the Golden Gun location has in the MWtGG scenario.
Weapon spawns typically have two accompanying ammo spawns. Make sure the ammo spawns are of the same level as corresponding weapon spawn! When placing ammo spawns, think about how much time the player will need to travel to reach it. You may decide to place ammo spawns in such a way that a player must choose between picking up ammo or proceeding to their destination along the shortest route.
There should be at least one weapon spawn of each level in the map. More often there are two or three of the same level, spread out from each other.
Once you have delicately designed your key weapon spawn patterns and the map feels balanced, you are faced with the player count problem. Because we can have so many more players, you need more spawns for players and more weapons for players. What to do about this is quite simple: place player spawns where you can, and give them a weapon and one associated crate as needed to ensure that no spawning player passes another spawn point before reaching a weapon. Choose power levels that are in accord with the path the player spawns on.
Armor is huge. Armor is vital to every player, and it causes the Black Hole effect, since there is a great reward for AC-10ing all day. Like with your Level 7 spawns, you want no fewer than two, and you want them spaced enough that everyone can get at them. For GoldenEye Source, I would like to see no fewer than three armors on every map. There should be two full armors spaced out properly, and at least one half-armor in areas that are far from both armor and a powerful weapon.