With an angle flip or a handy prop, you can make a portrait distinct and personal.
Ask your model to be in a contemplative state.
The eyes can betray a self-conscious disposition, especially during the first awkward moments of a shoot. Have your models think of something that puts them at ease. Better if they close their eyes; they may forget the camera and start to act naturally.
Take advantage of the bright sun.
The sun can soften an otherwise standard portrait. Also a good compromise if your subject does not like extreme closeups. (You make up for the lack of intimacy through texture.) You may also mimic the effect through intentional light leaks.
Position your subject close to the edge of the frame.
This clipped effect makes a photo look of-the-moment, as if the photographer has just popped in.
Do a high-angle shot.
This has the surprising effect of lighthearted intimacy. Not invasive but close enough to make a subject look endearing and friendly.
Add comic details
Some friends may be more comfortable being goofy. Other than on-hand props that exaggerate or support a humorous stance, you may also use ready-made backgrounds for contrast. Example: Pair an exclamatory sign with a play-lethargic expression.