These are general tips and guidelines but many crops will have a range of varieties for many different purposes, for example potatoes are categorised as first earlies, mid season and late crop but also into salad, new, bakers, general purpose and some will store better that others. Decide what is most useful for you according to your soil and needs. Most seed packets will have suggested sowing, transplanting and harvesting dates. Consider sequential sowings of things like lettuce and spinach to avoid a glut and keep cropping throughout the season – just a pinch of seeds at a time will keep you supplied.

Other useful links are:
RHS website https://www.rhs.org.uk/advice/beginners-guide
Sarah Raven https://www.sarahraven.com/advice
D T Brown & Co https://www.dtbrownseeds.co.uk/Home_2/growingrecord/ Free download to plan your growing season and record what you planted where and when to ensure a good rotation.