What are your custom setups for black Ops and what situations do you use them for?

I'm kind of a noob so I would appreciate a bit more detail in your answer like the game mode you play and what you use (gun/attachments/perks/equipments) and in what game modes. I mostly play TDM and FFA, not too much objective base. My K/D is below 1 most of the time...probably because I run around too much...I dunno what I am doing wrong...any help would be appreciated. Right now I am using Galil silenced/python with semtex decoy/claymore ghost sleight and hacker in a few FFA maches...I don't know the maps too well I just know that Nuketown is close quarters and Array is long...and I don't know how to switch between the guns I have for those maps