I've noticed that as I've started playing deathmatch more I have trouble mostly when people peek corner or wideswing or just full on run past the corner. Using the footstep noise I can usually predict pretty accurately when they will appear...

If you are one point off your ult and the only orb around is the weapon upgrade orb, you can drop your current gun and then consume the orb. That way you'll have both guns and can pick whichever one you want. Same goes for the golden gun...