I use a DM screen. Partly because it saves time having to look certain things up, partly because I keep my game notes back there where I don't want them seen (npc stats, maps, etc). If I'm sitting, dice rolls happen behind the screen because, well, it takes up the entirety of the little side table I use. If I'm standing, I'll just roll the dice on the map table in the open.
I will rarely fudge dice rolls, usually in favor of the PCs - my criteria for fudging is wholly fun based. If something happens that is amazingly, retardedly anti-climactic and un-fun, then I will fudge a bit in order to milk it for what little enjoyment is possible. For example, way back in the day, one PC is traveling between two cities and 'lo and behold gets a random encounter at night. Okay, a small pack of jermalane (sp~) sneak in and try to steal a few things. Pretty typical fare. PC wakes up, grabs his stuff and makes to get away. All well and good. The jerm throw a few of their little tiny darts as he flees. Now, by the rules we were using at the time (2e, combat and tactics critical hit rules) one of the little buggers tags the running PC in the head with a thrown dart that's about the size of a toothpick, and blows the thinking part of him half a block out the back of his skull. Screw that. The encounter was going swimmingly up until the how-the-hell-did-that-happen instakill, and so I fudged it some. The PC caught the doompick in the eye instead and was half blind until he could get it healed.
Fudging is like a gun - it's not evil in and of itself, it's how you use it that counts.