If using tomato puree in a stew-type dish, try cooking it gently with the vegetables after they have finished, but before adding any liquids, as it seems to deepen its flavour a little.
Always add garlic (or ginger) towards the end of the onions being cooked. I keep seeing people add them at the same time, but it will only cause a loss in flavour or increased bitterness if you cook them at the onion's temp for that long. They just need a light minute or two to remove the raw flavour.
If you use a lot of olive oil, keep two extra virgin olive oils, a cheap one for cooking and an expensive one for dressing. Try not to keep an opened olive oil for more than a couple of months, as it loses flavour quite quickly. You can buy ceramic bottles to decant it in, to prevent light damage, and to prevent as much air exposure by using a narrow pouring spout than opening a large screw cap each time. If you have some good oil that you want to use up, it works very well as an alternative to margerine or butter on slices of fresh or toasted bread. Pour it into a small flat tray (or a wide plate without much curve to its surface) and drag the bread across., This will absorb fully across the surface (if it's flat), but prevent any oil from waterlogging/dripping through the bread than if you drizzled it across the surface.
When cutting onions into strips, cutting across (against the grain) causes more damage to it, making for a stronger flavour, cutting length-ways (with the grain/top to bottom) produces a milder flavour. Additionally, cutting with the grain causes them to hold their shape for longer (best for caramelising), cut against the grain if you want them to dissolve into a slow-cooked sauce more effectively, or if you want a fresher flavour if using them raw or undercooked.
Canned tomatoes cooked for a long time don't require any sugar to sweeten them. You can add natural sweetness to tomato sauces by simmering with big pieces of carrot, then discarding them once finished.
If using dried pasta, check whether yours claims to be pressed using a bronze die or not. If it doesn't, look out for ones that claim that they have been, as it's generally a sign of better quality and there are appreciable flavour and texture differences between cheap and good dried pastas.
You can emulate the texture of minced meat in a vegetarian chilli by taking chickpeas or ideally kala chana beans (black chickpeas), and semi-mashing them.
Whole spices preserve much more flavour than powdered ones and are often the same price per weight or cheaper. Buy a cheap compact coffee grinder (this style for
example although the price is a bit high on that listing) or use a pestle and mortar, toast your spices gently in a frying pan, then use the grinder to powder them. Break up bigger things like dried peppers and cinnamon sticks with your hands to make it easier on the device. Even if you don't want to go the grinding route, toasted cumin seeds are going to give you lots more flavour than cumin powder. You can also toast pepper corns which adds a lot of value for limited-ingredient dishes where it is a primary flavour. This is one of the easiest ways to boost the flavour of your cooking without needing any additional experience.
You can make bomb rice for curries and other things by adding dried curry leaves/Asian bay leaves, a cinnamon stick, cardamom pods, etc in the water while cooking, then discarding at the end. This is also a very good way to use up whole spices before they lose flavour, and help you with your turnover. You can also use hing powder instead of turmeric for a more subtle yellow colour and substantially different flavour.
Cook meat in batches to avoid crowding the pan. If you are browning meat for a stew, use med-high (not maximum) to ensure you brown rather than blacken the surfaces, and avoid touching it until it needs turning over. If you're slow-cooking, don't worry about browning every side, the top and bottom should produce enough flavour, and the tenderness of the rest will be preserved. Browning all sides can be counter-productive as it cooks the meat too much. If cooking minced meat, still consider doing it in batches if it's piled too high, removing vegetables previously in the pan if necessary, and re-adding them later. The goal with cooking minced meat is to add it to a very hot pan, which will prevent it from cooling too much when the meat is added, then to leave it still to release any water and simmer it away as quickly as possible. Stirring or fussing around will just reincorporate the water back into the meat and further cool the pan, causing the meat to steam instead of brown, which is what gives you the dreaded grey mince look.
Use eggs and not cream in carbonara. Use a little lemon juice on your pasta if it doesn't already have a rich sauce (eg. meat/tomato). A garnish of capers is a great way to add freshness to light pasta dishes. If they're too strong per bite, you can cut them in halves or quarters.
If you have an iron casserole pot/dutch oven/ceramic-coated stoneware, consider oven-cooking meals that you would otherwise slow-cook in a sauce pan. The temperature distribution will be more even, and can produce very good results.
Buy a bottle of Asian fish sauce and add it to every stew you make (beef burgundy, chillies, ragus, etc). It stinks to high heaven but that smell will disappear after a few minutes and it adds an umami flavour that nobody will ever mistake for fish. It is a further more potent version of why people add Worcester sauce to meals.
Raise your dough in the fridge. There are still people who avoid making dough because they feel it can only make one big portion of something, but you can portion it off and rise it slowly for several days in the fridge to make multiple different things. If you want bread rolls for four days, for example, portion the dough into four, place three in cling film-covered bowls in the fridge (with a tiny amount of olive oil brushed over the top and bottom to prevent it sticking on both sides) for 1-3 days later, and rise the last in a warm room for using the same day. When using refrigerated dough, leave it out to warm to room temperature before cooking. Be careful about warming it too quickly near an oven/radiator/sunny window, as it can dry out. I personally put two in the fridge, and half-rise a third before adding it to the fridge for the next day to give it a head start, but this sounds like it could be a food hygiene risk that I am not aware of so don't listen to this part at all and if somebody can confirm or deny this I would appreciate it. Per Serious Eats it's fine to leave pizza dough for up to five days, and I have noticed a big difference in how easy a base is to stretch between 3 or 4 days of rising.
Buy a wooden spatula. They're much better than wooden spoons for scraping the bottom of pans while deglazing, flipping things over, etc.
Save your parmesan rinds in the freezer, and add one to a stew or soup to impart a little additional flavour and discard when finished.
Generally always favour chicken stock over beef, even when using in a meal with only beef meat, as for whatever reason chicken stock retains more flavour than beef, so offers more value and benefit. If you make small meals and find containers of stock too large for your needs, you can put them in an ice cube tray and freeze, defrosting a cube when needed.
If you have space in the freezer, save every carcass and bone you use in cooking, and you can make large batches of stock all at once to save some effort/maximise the amount produced. Speaking of freezers, they are most energy-efficient when full (a good excuse to cook big batches of food and freeze portions - Pyrex have great oven/freezer-proof containers with durable plastic lids), fridges are the other way around and are at their best when lowly-filled.
If you're cooking pre-packaged frozen oven chips and are having problems with the ends going too brown by the time the middles have cooked (a particular issue for me with thin fries), leave them on the tray/screen to defrost before cooking. they cook more evenly and quickly than when doing so from frozen. Also cook at the highest heat you can get away with as it'll give them less time to dry out and go crunchy.
The way to make your stir fries taste a little more like the nice takeaway flavours you might be trying to emulate is sesame oil. If you want something that you can use like soy sauce but tastes different (slightly sweeter/herbal), try ketjap manis.
