sharp creases on the edges between the mirror and the model for some reason i keep getting this raised surface in the middle of the face of my model. i checked the order of my modifiers and i tried smoothing it out, adding more edgeloops but that creates its own set of problems i found out. what i have been doing is manually adjusting each vertex but its a tedious task and feels very inefficient. also i don't want to have to do this for every organic model i create with the mirror modifier. also, i'm not sure if this is due to the mirror mod or the subsurf mod or if it's just me not placing the vertices in the correct spots.
There could be a face inside the mesh, right where it gets mirrored. That often causes some weird stuff to happen if you add another modifier