Let's assume you want some Earth like features (such as a day/night cycle)
In that case, you want an elongated orbit and a strongly tilted axis of rotation, such that 'summer' for one hemisphere is a long way from the sun, but for the other it is near the sun. So one hemisphere gets an extreme, if short, summer, whilst the other has a cold, long 'summer'.
(Bear in mind that we don't need that much of an elongation in orbit)
This still wouldn't be enough; we'd need a way of storing heat in the 'hot' hemisphere to get it through it's long winter, probably via shallow seas, and the 'cool' hemisphere could have extensive land/highlands with glaciers to reflect heat, furthering the North-South divide. This may bear some resemblance to Earth in the Mesozoic, with a large supercontinent (Gondwanaland) over the south pole and not so much land in the North. Even on earth today, the presence of Antartica means that the Northern hemisphere is ~2K warmer than the South.
So - a combination of orbital features, land mass distribution, albedo feedback and handwaving should do it.