The modes that are required for this achievement are as follows:
Arcade- Focus on your multiplier, do not allow enemies to pass. It will take at least a couple of stages to reach the silver medal requirement.
Wave- The enemies always come in the same pattern, so replay the first level a couple of times, to memorise their spawns. Shoot them as they're entering the screen for huge points.
Time Limit- Pick up as many of the yellow multiplier power-ups as you can, even if it requires you to rewind time. Make use of your fast forward power too, it gives you double the points when killing enemies (when in use).
Survival- Survive. Refer to "I'm a Survivor" for tips.
Tactics- Easiest of all the modes. Refer to "Tactician".
Score Attack- Same as Arcade, except only one level. Also, you get to choose which upgrade to bring. Personally, I think the chain shot or rapid fire are best.