There are various keyboard shortcuts that can be utilized for your efficiency in Adobe Premier. Here are some that I have sourced that should come in handy when I am editing:

Apply Video Transition – Cmd+D (Mac OS)

Apply Audio Transition – Shift+Cmd+D

However, the most useful tips I have found in my practice so far is the shortcut of marking in and out, as below:

Mark in – I

Mark Out – O