Hello Benny
1. Tell them ur gay... It calms them down straight away nd they feel more comfortable.
2. Dont do fake props... It feels fake. Take them outside and shoot pics while they not looking...
3. Be cool. Dont make it feel formal or ask them to smile cos I find those smiles usually suck...
Ok now we get technical:
1. If girls... Tone the sharpness of the camera done. With girls you want a soft outline and gentle backgrounds.
2. Play with colour. Contrast can be good.
3. Try neutral front on lighting...
4. Ask the girls to look at the camera and not at you.
5. Try get the girls to dress in clothing that is the same hue or colour...
6. Play with black and white and colour cropping. Can be good for the pic and looks modern...
Try googling Portrait Photography and you will see there are tons of tips out there. But most important I feel is to make them feel comfortable.
Mike