If you have a choice of mother plant, look for seeds from a 'Little Red' Oleander. It is the hardiest variety I know of. The only othe tips I have is to get fresh seed, plant in a warm, sunny spot indoors, harden off well before planting outdoors, and plant in a hot, sunny, sheltered, well-drained spot. Gritty soil at the base of a south-facing wall would be ideal.