three tables

Maybe it will be better to show all major tables here at once, so remembering can be easy:

• Present continuous:

  I	am	driving
  he/she/it	is	working
  we/you/they	are	doing

  
  
• Present simple:

  he/she/it	drives/works/does
  I / we/you/they	drive/work/do etc.

  
  
• Past continuous:

  I / he/she/it	was	playing doing cooking   etc.
  we/you/they	were

  
  
• Past simple: no such a table

My rule of thumb: there are 3 groups - marked above as
red(I), green(he/she/it), blue(we/you/they).

= In present continuous I is standalone.
= In present simple he/she/it is standalone (only this group has -s).
= In past continuous we/you/they is standalone (has were).

You can have your own rule of thumb for these tenses...