This simple but effective shot can be easily done by placing someone between you and the sun. Just position yourself in their shadow. The brighter the sun i.e less cloud, then the better the effect will look.
The best times to do it are sunrise and sunset but you can do it in the middle of the day when the sun is higher but you'll need to shoot from a lower angle like this -
A side on profile is best so that you can make out the features and tell who it is.
If shooting two people leave a gap between the faces to let light through and define the features of their profile.
Vary between close ups and further away. Use the editing options to increase the contrast which will darken the shadows. You can also increase the saturation if you have a sunset and want to give the colours some punch.
If shooting with a DSLR where you can control the settings, use a fast shutter speed around 1/200th - 1/500th seconds to reduce light on them and show the colours of the sky. Keep the ISO settings as low as possible and adjust your aperture accordingly.
For example, for this shot below I used 1/200th, f/9, ISO 200.
Now the sun should hopefully be making more of an appearance then you'll have some more opportunities to try them out in your garden.