Fill Gaps between Meshes with smooth surface I've been trying to attempt modeling on my own for my 3D Designs after going through tutorials, but I am having an issue smoothing the gaps between meshes. In the image below I have added to UV Spheres and molded them as I would like, but I am having issues smoothing the gaps between the two to appear to have one smooth mesh:

I have been adding vertices and faces manually, but the effect comes out very patchy. Is there a tool to help smooth this? 

NOTE: For those not familiar with the character in the background, I will include it below for reference:
It looks like, there are vertices connected with edges and a face on the inside of your model.

This could have happend, when you extruded a face and then cancelled the action. Canceling the action only reverse the move position, but would have given you an extruded face at the exact same position.

You have to remove any unwanted faces/edges and possibly reconnect your vertices in that area. To do that, in Edit Mode, switch to Face Selection Mode (in the menu bar of the 3D View). Then select one face after the other in that area and move them around (G). This way you could easily identify misplaced faces. Remove a face by  RMB selecting it and pressing X > Faces.