When plants are perhaps 4-8 inches tall pinch out the lead stem to encourage the plant to bush out. You may consider doing this more than once. Watch out for slugs and either control using a proprietary brand of pellets or whatever other method you prefer.
As the plant grows tie it into the stake you have set up already or if not carefully put on in place. Dwarf varieties should not need additional support.
Keep plants moist throughout and feed about once every three weeks with something like tomato feed or Miraclegrow.
Once buds appear increase this to weekly feeding. Keep your eyes open for mildew or other fungal diseases in warm damp weather.
Dead head regularly to ensure flowering throughout the summer and autumn