Sorting a table...

Hello all, I'm new to this list so forgive me if this question get's asked
a lot. (I did search the archives...)

I have a table of users where I store some basic info along with all my
authentication stuff.  I wrote a web interface in PHP3 for viewing and
modifying this table, my PHP page just goes through the table sequentially
from row 0 till the end displaying a good portion of the info on each line.
 Then, using radio buttons you select the user and the desired action,
click a button and then do your editing.  Once the user has completed the
editing, I perform an UPDATE on that row with the new values, but now that
row is moved to the end of the table, making the page that lists the users
list them out of order (one of the fields is a sequential ID number).  Is
there anyway to do a "sort by" or something similar?  Or do I need to set
the ID number to be some sort of index type?

Any help would be appreciated.

TIA!

-Jesse