Thanks to Instructor Matthew Harkins for providing the detailed count breakdown.
Introduction: A Newcomer level move for Foxtrot
Frame: Standard. Count: 1+2+3+4+.
Leaders and Followers: Leaders and Followers move the same.

Instructions (Leader & Follower Perspective)
For Feather Step, your right foot is the one that moves forward. For Three Step, your left foot is the one that moves forward. This will always hold true, for you cannot do feather step with your left nor three step with your right. The two main aspects this page will focus on is how to move forward and backwards with forward step. There is a very specific count you should follow for feather step, so read away.

Basic Feather Step is done Heel, Toe, Toe. As in, your right foot steps forward, landing with the heel. Your left foot then moves forward, landing on its toes and you stay on your toes. Your right leg consequently swings forward, landing with the toes of the right foot. From there, you'll then proceed to do Three Step.

Going Forward
1: Start with your feet together. On this count, release your weight. Your right foot will consequently slide forward, right knee more straight than bent. Your left knee will be bent. Keep in mind that your left knee should also go slightly forward. This is not a weight drop straight down, where your left leg stays in place and right foot just slides forward. This is a forward driving motion, which means both legs must have some forward movement.
And: Extend both legs to split weight position (remember from going backwards in waltz? if not, go and review). With your right foot forward and left foot back, both legs are straight. In addition, you're on your right heel and left toe. Difficult position to balance and be in, but you must hit it for a moment.
2: Begin taking right knee forward. Your upper body should be over your right foot at this point, but you should still be balanced and poised.
And: Collect the feet under your body. Weight is on your right leg as you prepare to drive your left foot forward.
3: Push with the right leg, thereby extending your left free leg into a split weight position.
And: Collect feet under the body, which means you are preparing now to have your right foot move forward.
4: Using toe pressure on the left foot, you allow your right foot to swing into split weight position.
And) Collect your feet under your body and lower.

Note that when going forward with Feather Step, you are in Outside Position, where you are stepping to your partner's right rather than in between their legs.

Going Backwards
We will assume your partner is executing Feather Step going forward. Going backwards is similar for both left and right sides, unlike say going forward (HTT for right side, HHT for left side).
1: Weight lowering. Left foot should be slightly back. Similar to moving forward, where your weight drop is moving forward and down, your weight drop here is moving backwards and down. Your body should not be left behind while your legs move to where they go. Instead, body and legs should move as a unit.
And: Split weight position. Even trickier than when going forward, but it must be done. Ball of your left foot, heel of your right foot.
2: Begin taking your right leg backwards. Upper body should be over your left foot at this point.
And: Collect feet under the body. Weight is on your left leg as you prepare to drive right foot backwards.
3: Split weight position, This time, left heel and right ball.
And: Collect feet under body.
4: Using the toes on your right foot, allow left foot to swing into split weight position.
And: Collect feet under your body and lower.

Notice the similarities between moving forward and backward? Yeah, you're in split weight position at the same times, moving at the same times. The reason for the very precise timing in foxtrot is that if you don't have perfect timing, it's very easy to unsync with your partner.

Tips and Tricks
  • HTT: Right Heel, Left Toe, and Right Toe. This particular combination of HTT is for the purpose of going into outside position with your partner and also achieving the loping gait of foxtrot.
  • Arm Swing: A way to help you practice achieve the pendulum motion of foxtrot is to when doing Feather Step, swing your left arm forward. On the first step, your left arm is coming down. On the second step, your left arm should be at about shoulder height. On the third step, let your arm stay up there as long as it can until it needs to come down (like a pendulum).
  • Split Weight: Your weight is literally split between your feet. Directly in the center between the two. Work on maintaining this position in order to be able to slip in and out of this position.
  • Sync: As said above, make sure to have timing down perfectly. Otherwise, if you're in split weight position while your partner's already moving to the next step, you're going to simply fall over and that's awkward.

Advanced Concepts
  • Sway: Yeah, you thought we only had this here in Waltz?'s here in Foxtrot too. Sway in Foxtrot is basically the arm swing described in T&T above, but with your body instead of your arms. The reason being because your arms are occupied remaining in frame with your partner but your body is free to apply sway.
  • MotorBoat, Sailboat: A good characterization of Foxtrot steps is that when going forward, the first step is like that of a motorboat as you're providing the power to move forward. The next two steps are that of a sailboat, you're just floating along toes. The same is true when going backwards.