One of the new additions to Resident Evil 6 for the PC, PS3, and Xbox 360 are the skills and skill arrangements. You can select up to three skills at once, which is why having more skill arrangements to set and select from on the fly can be extremely helpful.
You can gain the ability to set up to eight skill arrangements, that you can change on the fly in campaign mode. This can give you a much better tactical advantage, allowing you to set specific skills for certain scenarios you come across in the game.
To unlock these eight skill arrangements, you just need to complete a story campaign for any of the three default characters.
Check out my other article for a complete list of cheats, unlockables, tips, and tricks for Resident Evil 6.