It sounds obvious, but be sure to go for something you like the taste of, and in quantities you can reasonably get through. I say this from experience: there is no point in filling a two-litre Kilner jar with pickled, skin-on kiwis if you are the only one who is going to eat them. Use small jars. Use flavours you enjoy. The point is not to waste anything.
Be sure to clean hands, surfaces, utensils and produce thoroughly. Wash all jars, bottles and lids in warm soapy water, and rinse thoroughly. They need to be hot, dry and sterile when you fill them. So, for preserves you intend to use up quickly, place your jars (without any rubber seals) in a 140C (120C fan)/285F/gas mark 1 oven for 20 minutes, timing it so that they are ready when your product is. And top whatever you are storing with a circle of wax paper before sealing.
There are the more pungent varieties that take time to mature. Some version of cucumber pickle is found in most countries, but everything from green beans to new peas work too. For Iranian torshi bademjan, aubergine is first parboiled in equal parts vinegar and water, then squeezed, sliced down the middle and stuffed with garlic cloves, dried mint and a little salt. Pack tightly into a jar small enough that the pickling liquid (125ml fresh cider vinegar to 1 tbsp boiled and cooled water) covers the veg. Seal and store them in a cool dark place for at least a month and keep in the fridge once opened.
Fruit, too, loves to be pickled. Hugh Fearnley-Whittingstall bottles cherries – stones, stalks and all – in a hot syrup (200ml water, 300ml white-wine or cider vinegar, 250g caster sugar, 6 black peppercorns, 3 bay leaves, 2 juniper berries, and 2 cloves) and leaves for a month before using. Nigel Slater uses a similar syrup for stone fruit, but cautions that since no amount of vinegar will soften hard fruit, it’s best that peaches be first stoned and parboiled, then skinned; with apricots, he leaves the skin on. Conversely, these pickles are ready within three days. Which is to say: follow recipes carefully. Don’t skip any steps and stick to all specified timings.