READABILITY:
~~~~~~~~~~~~~~~
Does any part of the story drag?
Are there parts that you skipped to get to ‘the good part’?
Did the author over-inform (info-dump) anywhere?
Did you understand every phrase / term which was used?

Did any parts seem confusing?
~~~~~~~~~~~~~~~
FLOW:
~~~~~~~~~~~~~~~
Does one scene lead logically into the next?
Do the scenes flow smoothly from one action to the next, or did they jump as though something was skipped?
Is there enough downtime between intense scenes to allow it to build to the next?
Did you have to reread any part of the action sequences to understand who was doing what?
~~~~~~~~~~~~~~~
DIALOGUE:
~~~~~~~~~~~~~~~
Does the Dialogue sound realistic for the individual characters?
Could you see what the characters were doing while talking?
Could you see where the characters were while talking?
~~~~~~~~~~~~~~~
CHARACTERS:
~~~~~~~~~~~~~~~
Could you see what each character looked like clearly?
Do their actions and reactions seem logical and realistic?
Could you feel the emotions between the characters?
Does the story stay focused on my main character?
Were any of the characters too much of a jerk or too aggressive?
Were any of the characters whiny, wimpy, or overly dramatic?
Are any of the characters too stereotypical?
Who did you like best and WHY?
Who did you hate and WHY?
Who got on your nerves and WHY?
Do any of the characters get in the way of the STORY? 

This list was taken directly from the Goodreads Beta Reader forum:
https://www.goodreads.com/topic/show/18274464-beta-reader-checklist