Realtime view in edit mode.

I believe this has been asked before but I couldn’t find it so sorry for asking again.
How can I view and edit my models mesh in realtime?
EX: I make the mesh, move with an armature and see a small glitch. I attempt to fix it using the shape modifer(the quick way). But in edit mode, the mesh is in the original position and not the position I need it in to make the corrections.
I know there is a way to do this, I just can’t remember how to do it.

you can edit the vertex groups while posed in weight paint mode [choose it on the 3d header, like you could choose edit mode]

You can do this only with 2.4. You need to use an armature modifier which is enabled for editmode and also applied to editing cage. If you use a subsurf modifier it has to also have those attributes active. Like this:

But fixing a “glitch” in the deformed state can create a new one in rest position, so you might want to try to fix it first with weight painting. If that is not enough, you can add corrective shape keys driven by the rotation of the bone: