Can getting twins be planned.

No: Cant plan twins and in reality, though most due fine, there are higher risks, it is very demanding and generally not desirable once your there. Good luck.

Yes & no: If you go to a fertility center and have eggs harvested they can fertilize them with dads sperm and implant as many as you want. It may not work but you can start out with a better chance of twins than the random lady gets in pregnancy. On a practical sense, you can't plan it. No diet, position, timing, etc. will get you there.