An easy way to liven up the half & half, the 5/4 waltz of the mid-1910s, is to vary the promenade. 

In the basic half & half promenade (previously described here), the dancers take ballroom hold and both face line of dance, gliding forward side by side with half & half step patterns (1…4-5, 1…4-5). 

The second edition of the 1914 compilation Dance Mad offer two easy ways to vary this promenade:

In the Quinlan Twins' description of the half & half, the eighth figure is a more elaborate promenade that alternates dips and foot lifts:

123    Step forward (gent's left/lady's right) and dip to the floor
45      Walk forward two steps
123    Step forward (gent's right/lady's left) and raise free foot to 4th position forward
45      Walk forward two steps

Leading the dip is easy, though the gentleman should be careful to guide the lady down gently, taking a long step (lunge) with torso vertical rather than bent forward, so she does not feel like he is pushing her face-first into the ground.  To lead the second measure, simply tilt back lightly on the first step; the raising of the free foot must be caught visually by the lady.  Repeat the pattern a few times so that she has a chance to perform it correctly.

The Castle Assistants take a different approach in "Step Six" by adding a hop to the standard promenade:

123    Step forward (gent's left/lady's right) raising free foot behind and making a slight hop
45      Walk forward two steps
123    Repeat on second foot
45      Walk forward two steps

Leading a hop is easy: just hop at the appropriate moment.  The lady won't catch it the first time, but she will on the next repeat.

They also offer a second version with the foot alternately raised in front and behind:

123    Step forward (gent's left/lady's right), raising free foot forward and making a slight hop
45      Walk forward two steps
123    Step forward (gent's right/lady's left), raising free foot behind and making a slight hop
45      Walk forward two steps

The first half of this pattern just adds a hop to the second half of the Quinlan Twins variation above and is led the same way, with a backward tilt.

All three patterns can be mixed and matched, but be careful to repeat each one enough times in succession for the lady to do it successfully.  Switching patterns every two measures will just be irritating.

Source for these variations for the half and half:
Dance Mad, second edition, [edited] by F. Leslie Clendenen, St. Louis, 1914