Yes, the size of baking trays is not standardised. Therefore, when buying, make sure that the tray has the right dimensions for your oven.
If in doubt, measure the old tray and use the values as a guide.

Butter and margarine are best suited. The fats should be as soft as possible so that they can be spread well. When they are at room temperature and spreadable, use either your fingers or a paper towel to rub them on the baking tray. Don't forget the edges.
You can also melt the butter or margarine and apply it with a pastry brush.
Add a little semolina, flour or breadcrumbs to the greased tray for an extra non-stick effect and to make your baked goods even easier to lift out.

If the tray is not very dirty, you can simply clean it with warm water and washing-up liquid. Some baking trays are dishwasher-safe and can therefore withstand cleaning in the dishwasher. For more stubborn stains and burnt-on stains, you can use home remedies that you will find in your kitchen anyway.
For example, if you spread salt on a baking tray and put it in the oven at 50 degrees for about an hour, it will help against burnt-in food. If the salt has turned brown, take the tray out, shake off the salt and wipe the tray clean.
Another trick is baking soda. Just put some water on the baking sheet and let it soak for a bit. Then pour a packet of baking soda into the water and let the mixture soak in. Afterwards, you can simply wipe off the loosened dirt.
Dishwasher tablets also work wonders. Fill the tray with boiling water, dissolve a tab in it and put the tray and water in the oven for an hour.

Metal expands with heat. If the heat is not distributed evenly or there are temperature differences, for example because you put a frozen pizza on the preheated tray, it may warp.
Therefore, load the tray evenly and do not leave it in the oven during preheating.

In addition to baking trays, oven racks are also suitable for preparing food in the oven. If you mainly use oven dishes, for example for casseroles or braised dishes, they are even the better choice. The strut construction allows the heat to reach the bottom of the dish better, which means that the contents cook faster.

As a rule, baking trays are made of recyclable raw materials. The best way to dispose of your old baking tray is to take it to your local recycling centre. If you live in an area that has recycling bins, you can simply drop it off there.
If this is too inconvenient, put it on the street at the next bulky waste collection.
The residual waste bin is not the right choice. If you put old baking sheets in there, they go straight to the incinerator and the opportunity for environmentally friendly reuse is not taken.