Test result tells me how should I change what to describe. As we play alot and for a long time my players know what to watch out for when I change my voice or style. If thats not enuff I describe more or let them have it

Some traps you cant avoid just with Ini test (some traps have much too low Ini stat or in case of Pit Trap you can try to avoid falling only if you have spear, staff or a hook), I judge it on how they work in RL. If you spot before you trigger most times you are fine.
As for Magical Traps most of them are hard hitting so I let to test Steel Thought even if "Suprised" with no penalty to MD( but I dont describe whats happening exept: "There is some magical force that wants to influence you"). Most ST users are weak in combat so going first is a risk as ambushes happen.
I dont like to kill my PC, so many times making dmg test I lowered it to harm them bad, but not to kill them (but never if they knew there is a trap, then dice decide).