One of the main reasons for using a greenhouse when growing tomatoes is because of the climate you live in. If you cannot guarantee warm sunny weather for your tomatoes then you will need to consider using a greenhouse, this will help you control the climate for the tomato plants and give them a better chance of producing lots of edible fruit.
Clearly planting tomatoes in a greenhouse leaves you with limited options, for most people the greenhouse will be relatively small and probably only a little taller than the height of an average man, unless of course you have the space and money for a large more industrial sized greenhouse, but for the purposes of this article I am going to discuss the smaller option that is, I believe, more prolific in the home gardening environment.
This makes it much more difficult to use the tomato plant hanging option for your plants and in practical terms the only real option you have is to plant using the soil inside the greenhouse or to sit pots on the floor of the greenhouse, either way make sure you have a good mix of mulch, compost and fertilizer.
You will still need to be able to support the fronds of the tomato plant and with limited space a good way of doing this is to knock 3 stakes into the ground at each end of the planned run and to tie gardening string between the stakes. When the plants grow they pass through the strings and then hang over them a little like clothes on a washing line.
If you are inside a greenhouse the plants will be totally dependent on you for their water so you have a choice, invest in a self watering system or use hand watering. If you choose hand watering it is also good practice to leave the water in the greenhouse with the plants to allow it to warm a little before use. Takes a bit of discipline but as long as you refill after watering then leave overnight, that should do the trick and you will not shock the plants with cold water.
The final thing you need to take care of is not letting the greenhouse get too hot and or humid, if it is really sunny for a period you can paint the glass with a whitewash to reflect the sun away and you can open the roof light or door to let some of the heat get away but don’t forget to shut them again at night when it is cool.
Other than these few peculiarities the tomatoes should be treated in much the same as they would be if they were being grown outside, so in addition to proper soil preparation and watering, you need to take steps to keep them disease free, pest free and to give them access to plenty of nutrients via a feeding program.