Cook the pasta in a large pot and make sure there is enough water in it. It will prevent the pasta from being sticky. You can also add a spoon of olive oil in the boiling water, this also prevents the pasta from being sticky.
Make sure the pasta is perfectly cooked. Boil it according to the time given in the pasta packet. Overcooking will make it sticky and as a result, it will loose it’s texture.
Don’t overcook the roux as it will spoil the texture of the sauce.
While adding milk, continuously stir the sauce or else it will form lumps.
Overcooking the vegetables will result in loosing the crunch in them.
While preparing the sauce try to keep the flame at low to medium.