At its best:
When planting, ensure that the joint where the roots meet the stem is facing upwards. Label your pots and grow on in a greenhouse or sunny windowsill. Keep the tubers well watered.
Pinch out the tips of the main shoot, down to the top pair of leaves. You also need to remove most of the shoots growing from the tuber, except for five. This encourages bushy plants, strong, vigorous growth and a lot more flowers.
When all risk of frost has passed, harden off plants by placing them outside during the day and bringing them in at night. After a week they will be ready to plant out into their final growing positions.