If you are doing a crouch start without blocks try having your feet 1 1/2 and 3 foot lengths respectively
back from the start line.
When the gun goes to start the race the aim is to drive
out hard from the blocks, with relatively short fast strides to build up speed quickly, without
standing up straight. It should take about 30m before you are in your full
running action and standing upright.
As your hips form your centre of gravity it is useful to think of forcing them
forwards and only slightly up as you build up speed. It will also help to
drive your arms fast to build up speed, as you legs will automatically follow.