Vegetables are extremely versatile; most can be eaten raw, and they can be cooked by virtually every method. All vegetables should be washed thoroughly before use, to remove dirt and traces of pesticides. Peeling vegetables is an easy way to remove surface dirt or germs, but don't peel too thickly because many nutrients are stored just below the skin. Some organic vegetables can be treated to a good scrub and do not require peeling.
How long you cook vegetables for is really down to personal taste - but bear in mind that the longer you cook them the more nutrients will be lost. Nowadays most people prefer to cook vegetables lightly, leaving them brightly coloured with a little 'bite'. As a general guide, most leafy greens, brassicas, pods and seeds and stalks and shoots will take about 3-5 minutes to boil, about twice as long to steam. Roots, tubers and squashes (but not courgettes, which cook very quickly) will normally take 10-20 minutes to boil, depending on their size, and slightly longer to steam.
Check to see if vegetables are done by piercing them with a knife or tasting them. Drain them and serve at once. If you want to serve them later, plunge them into cold water to stop them from cooking further then cook again very briefly in boiling water when you're ready to serve.
Because of their natural sweetness many vegetables are used in desserts, for example carrot cake and pumpkin pie.