The first thing to do is to try to remove almost all the crusted and scorched food residues using kitchen paper and, if there are still residues as it often happens, you need to put in the pot (or in the pan) hot water with detergent for dishes and leave it for a few hours.
After a while, using a non-abrasive scourer or sponge (depending on the type of material of the pot or the pan and if the internal coating is non-stick or not), try to remove the encrustations from the bottom as much as possible.
At this point, there are different procedures for effectively scraping and cleaning a burned pot. Here is the most reccomended for obtaining the best results in the recovery of pots and pans so burned on the bottom that they seem to have become useless.
If the incrustations are superficial and the pot has just few burnt areas, the best thing to do is to fill it with water, add 1 tablespoon of sodium bicarbonate and a handful of coarse salt, bring the water to a boil, let it cook for half an hour to low flame, switch it off, let it cool and then proceed with the removal of any residues.
If, however, the pot or pan is really battered there is an old grandma's remedy: fill the pot (or pan) with cold water, add 2-3 tablespoons of sodium bicarbonate, 1 glass of white vinegar (the doses are according to the capacity of the burned pot or pan), let it boil for about 1 hour and let it rest until the liquid becomes lukewarm. Then proceed with the removal of any blackened residues and, if they are hard to remove, repeat the whole procedure once or twice.
If the encrustations still resist, bring the water to a boil with 1 handful of coarse salt and 1 handful of sodium bicarbonate for 1 hour and then let it rest for other 24 hours before proceeding to stroke any burnt residues.