This is a list of the most helpful keyboard commands I use within top.
h shows help on interactive commands. Also see the top manual page
q to quit the program.
Up and Down to scroll through processes one by one, or PageUp and PageDown for paged navigation.
Left and Right to navigate horizontally through fields (in case you're displaying a bunch).
Shift+c will show an index of where you are in the process list (eg 30/300 when your cursor is on process 30 and there are 300).
Shift+p sort processes by CPU usage
Shift+m sort processes by memory usage
Shift+r reverse sort order
Sort on any field: Press f to bring up the Field Management menu. Select the field to sort on, press s and then Escape.
Shift+l search for a string and highlights all occurences
o add a filter to limit which processes are displayed. A filter takes the format {field name}{comparator}{value}. For example, to see only processes owned by my user, I would add a filter USER=eric.
Ctrl+o view active filters.
= clear all filters.
m switches memory views between the list of metrics and graph view.
k kill a process
d set the refresh rate (in seconds)
Shift+w saves the settings you've configured while running top to a file (.toprc) so they persist next time you use it.
Shift+e toggle the scale of memory metrics (between kilobytes and megabytes etc.) in the system memory summary, and e toggles the scale of memory metrics in the process list. The default is kilobytes, I find megabytes a useful level.