Premiere - Easy way to extend last frame of a video clip
What I usually do ... 

Locate the frame in the clip you wish to extend, hit C, the razor tool, cut the frame. Then right click on the cut clip and select 'frame hold' 

A popup menu appears, Select hold on, in point (the start of the clip) and select OK.

Then just drag and extend the selected clip for as many additional seconds you wish to extend it for.

Normally I would also unlink the clip before cutting so I keep the audio separate.

Edit:
For CC there are a few more options in the menu to freeze frame the video
You can see here:
http://creativeclouduser.com/creating-freeze-frames-in-premiere-pro/