issues after duplicating geometry

Hi new here and my first post.

I am using blender 2.79 release candidate 64-bit and I am have a few problems in edit mode, most specifically with vertices and edges. I am building some game assets at the moment and I am doing a lot of duplicating of pieces of geometry.

Whenever I do copy and then drag a piece it always ends up misaligned to the rest of the geometry, so then I have to go through and delete vertices/faces/edges, delete doubles and then select the edges I want to ‘bridge edge loops’ on, and then it’s all good.

I am coming from 3D Studio max, so I am still learning the workflow of blender. Should I constrain the geometry to an axis when moving it so it doesn’t go out of alignment when I switch views? I will give this a go now, but would appreciate any tips on this.