::Whore the armor
Never let your opponent get it, even if you already have 150 armor grab that vest anyways.
::Don't be afraid to run
If you're low on health and have the opportunity to get away and grab health/armor then do it
::Bind some keys
Make sure you have binds for throwing weapons (in case you're low on ammo) and maybe even a 'select best weapon' bind
::keep moving
Camping is not only lame but once you're found you've been sitting so long you won't be used to getting your arse out of the way of a combo
::Spam
Spamming in 1v1s is perfecly fine and not considered lame. spamming shock balls can save you many a nasty combo and using rox/flak can weaken armor significantly
::Know the map
Make sure you know the map as being new to a map won't help you armor whore which is critical to DM
Hope those help you out if you keep playing 1v1s
