The seeds are ripe when the pods begin to split and show the little black seeds inside.
Sow the seed fresh. It germinates better straight from the plant rather than being dried off.
Cover lightly with grit, gravel or whatever rather than compost.
Sow in a deep pot rather than a seed tray (reasons later).
Leave exposed to weather. They need a period of cold followed by warmth to initiate germination.
When (if?) they germinate do not be in a hurry to p rick them out. This is the reason for deep pot rather than seed tray. They have only one root to begin with and if it is damaged, it dies and a new one has to be produced from the base of the seedling, usually they die.
Feed the seed pot with dilute Baby Bio type stuff, until the leaves go yellow then allow the pot to dry off.
Repotting may be done when they are dormant. Some types never really go dormant so be careful.
I often do not repot until they have had another seasons growth. Remember many of them actually grow in late winter/early spring.
Cannot think of anything else for the moment.
Not as hard as it seems. Big ones take a few years to reach flowering size.

I agree with the above. Having said that if you dont dead head them they will drop their seed and they will grow where they land. good in some ways but you then end up with too many . I ade the mistake of that and every year I find them where I dont want them.