Question(teleports and walkover doors)

ok im just starting out i got doors to work. but i want to be able to have an item on the ground and once they get it doors on the side of the room open up but how do i make the door know that when i walk over a specific tile that it will open. The same question with teleports how do i specifie where i want it to go. I know about the item teleport destination but when i put 2 on there it switches between each spot. How would i make teleporter 1 go to spot 1 and teleporter 2 go to spot 2? Thanks in advance

There are three types of linedef triggers:
W, which means its triggered by walking over the line.
S, which means its triggered by pressing the line.
G, which means its triggered by the impact of your hitscan weapon (pistol, shotguns, chaingun).

Your editor should make clear note of these. Also, all linedef types have a certain number of times they can be triggered depending on whether they have a "1" or "R" beside the "W", "S", or "G".
"W1 Open Door Stay Open", for example, is probably what you want to use for your trap. Just make some invisible lines around your booby-trapped item, and set the tags.

All linedef types, aside from a few doors, require a sector tag, which tells the game which sectors to open, move, etc. All you need to do is assign some abitrary number (that you've made up), to both the linedef tag on the sector, and the sector tag on the linedef. Whenever you activate the linedef, it will affect all sectors with that tag.
In the case of teleporters, the sector tag (on the linedef), points to the sector with the teleport destination.