Best for what? Size of crop? Taste? Simple success?
Outdoor tomatoes in the UK are likely to suffer from blight sooner or later in the season, so if possible grow them under cover. Even a 'cage' covered in polythene will be better than nothing at all.
You need to pinch out the sideshoots as GD is a cordon tomato (indeterminate).
Gardeners' Delight is one of the best tasting small tomatoes, so you shouldn't have too many problems, but always grow in the soil (with a large planting hole into which you have mixed some good potting compost.) in preference to pots and bags which are difficult to keep watered and fed well unless you have the time to do so twice or so a day.
Once they start fruiting, as tomatoes like lots of rich feed, water them with a liquid feed, either from a garden centre or just as good from a homemade mixture, like nettles or comfrey soaked in water for a couple of weeks, or just a bag of manure suspended in a bucket.
Keep them on the dry side for the sweetest fruit. Complete drying out and then watering will cause blossom end rot (dark patch on the fruit) though much more rarely on GD than larger tomatoes.
Lastly, when you have your mammoth crop and can't eat them all, try drying them for winter use. Cut each in half and sprinkle lightly with salt, then either place in a warm sunny spot (in the barbecue summer the UK will undoubtedly have this year if the Met Office predicts lots of rain) or in a VERY low oven.
Pop the dry tomatoes in a freezer bag and in the freezer and rehydrate them when you want to use them in the winter. Delicious!

Hello, generally the growing of all tomatoes is straight forward irrespective of type.Obviously if you are growing from seed different types are sown at times stipulated on the packet.ie some are early fruiting and therefore propigated earlier,some main crop and some fruit later.Gardeners Delight are main crop and a good variety to grow for a reasonable crop.If I remember correctly I used to propergate these in late March to get a good crop in August/September.
If we still have late frosts I would propergate them on windowsill.I take it you have a greenhouse ? As I'm sure of the size I suggest two options, 1. Grow two plants per 25/40L compost bag,lay bag flat and cut two circular holes in which to place plants in.When first fruits appear on truss(branch) start feeding a general feed, Tomatorite or Chempackare ok.
2. Plant in bucket size (approx 10L/15L pots).If you have these this would be the cheapest option. Mix a general compost with some organic compost or manure. Fill bottom half of bucket.Top rest up with general compost and plant.Feed as above.It is best to feed from the bottom and let the plant search for feed/water.Feed every week.Watering MUST be regular or fruit develope
black spots on the underneath of fruit. I have had excellent results following this method and wish you sucess in growing your own.