A selection of hints and tips (in no particular order) which have served me well in the kitchen over the years. I make no claim for originality about these observations, and I would certainly agree that most of them probably count as simple common sense. But worth noting down, I think.
Boil a Kettle. It is amazing how often hot water is required in a kitchen, whether to thin down a soup, stew, sauce or gravy; to top up boiling potatoes, rice or vegetables; or to warm up the washing-up water. When entering the kitchen, make it a habit to fill (at least half-full) the kettle and set it on to boil.
Cooking should be fun. Cooking for yourself - or friends and family - should be relaxing, fun in itself, not a chore. If you're not enjoying it, don't do it - buy ready meals or go out for dinner. But if you are in the kitchen, then enjoy the experience. A little light music, and perhaps a glass of wine or beer to hand, too?
Quantities.
It's far too easy to cook too much, particularly if you are only catering for one or two people. This is just wasteful, and there's also the danger of eating too much and putting on weight. So, consider cooking quantities which err on the small side and, if you are really still hungry afterwards, enjoy a second course - a dessert, fresh fruit, or even just some cheese and biscuits.
Be sparing with the salt. These days, the danger of too much salt in one's diet is increasingly well understood, and it seems to be good advice to keep down the amount of salt wherever possible. Of course, this can mean that the food tastes rather bland, so try using more herbs and spices, or even freshly-ground black pepper, to zing things up instead.
Cooking Pasta. It really is very easy to cook spagetti or other pasta. You need the biggest pan you can find - huge! - and half-fill it with water. Add lots of salt (most of the salt stays in the water) and a tablespoon of cheap olive oil (which stops the pasta from sticking). Make sure it is thoroughly boiling before you add the pasta. Keep it boiling, and stir occasionally as the pasta cooks.
The best way to find out if the pasta is ready is to fish out a bit and taste it - don't bother with all this "throwing a piece of pasta at a cold plate" malarky. When cooked to your taste, remove the pan from the heat, top up by a third again with cold water from the tap, then immediately drain by pouring into a collander. Eat as soon as possible.
Cooking with Eggs. Eggs are quite delicate things - apart from the shells, I mean! - and are worth treating with respect. Buy the best-quality eggs you can afford - you really can taste the difference. Make sure you take the eggs out of the refrigerator at least half an hour before you want to cook them.
The white and egg-yolk parts cook at slightly different temperatures - that's how you can get soft-boiled eggs - so eggs should always be cooked slowly and gently. Most egg recipes reply on getting plenty of air mixed in with the eggs - beating and so on - so don't stint on this. Using a mixing machine (boy's toys!) saves your effort.
Wooden Spoons: I prefer to use wooden sppons and spatulas for most cooking purposes. These tend not to damage the inner surfaces of the pots and pans, and they seem to clean up well enough in the dishwasher.
Be careful not to leave the utensil in the food while it is cooking, however, since it will tend to taste the food. I also like to use a wooden fork for making scrambled eggs.
Re-use Jars. Jars which used to contain jam, or instant coffee, or pickles can all be re-used in the kitchen. Make sure they are thoroughly washed before re-use - you don't want everything tasting of vinegar, do you! Running the jar (and lid!) through the dishwasher a couple of time works well - this also tends to remove the labels, too.
Once a packet or rice - or pasta, or sugar, or nuts, or whatever - has been opened, transfer the remainder to a clean jar. Use a marker pen to label it - so you can tell what's inside easily!
Jars like this are also good for making up Salad Dressing or marinades (for Duck Legs with Cherries, for example).
Timing. This is one of the skills of cooking and worth practicing. The objective is to get several things - a main dish, vegetables and a sauce, perhaps - to be all ready at the same time. Of course, you can keep things warm in a low oven, for example, but most food is best when served as soon as it is cooked. Timers which go buzz or feep at the set time help a lot, too.
Warm plates and bowls before serving. Tepid food is generally horrid - it should be either as hot as Hell, or as cold as Charity - a saying I attribute to my Mother. So warming the plates and serving dishes keeps the food hotter for longer. A plate-warmer as part of the oven is great - or you can just position the dishes on top of the cooker, or in the grill area, where the heat from the oven and rings will warm them gently. Don't get them too hot, though, or they might break.