my tomatos flower but few tomatos

Usually tomatoes not setting are due to 'dry set' caused by extremely hot dry conditions or lack of pollination, though tomatoes self-pollinate.
Some advise tapping the plants at midday which helps disperse the pollen.
If you have been enjoying/suffering extremely hot dry weather, try spraying the tomato flowers with water to help them set.
Are you growing them on a single cordon (stem)? This enables the plants to be more manageable and helps with ventilation. If on a single stem, only remove leaves if they become yellow or diseased, and below trusses, but regularly pinch out any sideshoots.