The three biggies I remember from growing carrots:
1) the soil needs to be very sandy and no rocks, or you'll get forked carrots
2) in the UK they have carrotfly (unlike in the USA where we do not). Plant or keep near something heavily scented, like garlic chives, to dissuade carrotfly. (Apparently they find the carrots by scent.)
3) they are very hard to germinate - it helps to cover the soil with wet newspaper and then keep it damp. Once they sprout, you would want to remove the newspaper right away.
Have fun!