More at http://orgmode.org/manual/Clocking-work-time.html
Create a section with a name matching the task you’re about to do. Place the cursor in that section. Use the following hotkeys to clock in or out:
C-c C-x C-i: clock in C-c C-x C-o: clock out
To change a timestamp after it is inserted, place the cursor on the element you wish you change (year, month, day, hour, minute) and click S-up or S-down.
C-c !: insert time stamp w/ date C-u C-c !: insert time stamp w/ date + time
C-c C-x C-r: generate report C-c C-x C-u: update report (place cursor at #+BEGIN first)
Adjust :maxlevel to get more details
If the you’re is emacs idle in org-clock-idle-time minutes and a clock is started, emacs will prompt you on what to do with the idle minutes.
k: keep some or all minutes K: keep some or all minutes and clock out s: keep none of the idle minutes S: keep none of the idle minutes and clock out g: “got back” X minutes ago G: “got back” X minutes ago and clock out C: cancel the clock entirely