1) Do you mean constrain edges to faces while you slide them around? If you're using 2008-09 look for "Constrains" check buttons in the Edit Geometry Rollout, else its a drop down. 2) I think you're looking for bridge if you want to create new polys across a gap. Or Weld & or Target Weld to join one edge to another. I…
1) shift+x when in edit poly is the hot key for that I think. As vig said, it will let you slide edge loops around while constraining to the shape of the mesh. -Tyler