THE PUSH-UP

I think every woman should do push-ups everyday.  It is one of the greatest moves for toning your arms in the whole world.  Especially when you vary your hand placement and speed of the push-ups. 

 Also - the majority of women cannot do very many regular push-ups (me included).  For toning purposes, it is better to do more push-ups girly style (on the knees).  MAKE SURE to keep your ABS TIGHT (pull that belly button into your spine) and TIGHTEN those BUNS!!!
  Various hand positions: Normal (shown above), wide, narrow (make a triangle with pointer fingers and thumbs).   Burn your triceps by keeping your elbows close to your body as you lower your body. 
Different inclines will also target different muscles: use your counter top or put your feet/knees up on your couch and do push-ups - and pretty much any other angle you can think of.

20 - 30 reps.  AT LEAST 3 SETS. 

Another variation is the shoulder push up - this still works most of the arm muscles but also targets heavy on the shoulders and lats.   Its pretty much a push-up in downward dog.  Bend those elbows and touch your head to the floor . . . or as low as you can and still get it back up.

Smaller muscles doing the work so 10 - 15 reps, 3 sets.