I plant mine out from March onwards, although last year i did an experiment to see if they'd be okay planted in February and they were, the 2 i planted then were glorious.
I leave mine in the ground all year round now.

Bear in mind the different parts of the country though, varying climates throughout.

As to the mthod, i simply plant mine straight into the soil, no fancy treatment.

If you want to start them off in pots(they often flower sooner than those left in situ) plant them just below the surface of the compost (use fresh) and water lightly. They won't need any more water unless they get very dried out. As the new shoots come up give more water. watch out for slugs! Keep the pots inside if possible, but remember to harden them off before planting out.

Thanks you both, as Im in the North East I think maybe Ill put them in pots first and plant them out early May Ill be on my hols from the 25th so I need to get them in, Ill just watch the weather I think!! and slugs are a problem I dont put pellets down seeing as I have two little dogs, I might try putting something like sharp sand around them that might help.

I always wait till the frosts have finished and then put some in pots and some in the garden.