My oven is self cleaning, but needs to be pre-cleaned first - how???

By pre- cleaning I think they mean clean up all the burnt bits, etc. before you start the self clean cycle. Read the instructions that came with the oven or go online with the make and model and find out it says to take out the grates or not.

All the manufacturers call for is the "heavy, crusty" stuff to be pre- cleaned.. I normally use a dish cloth or towel soaked in hot soap and water with ammonia @ 1/4 C .. lay it on and let it soak... once it is sort of soft... scrape it off. If the stuff is really gross you may have to use commercial oven cleaner and let it sit over night... using the self clean can make it harder to remove... The Mfg's also say to remove the oven racks... I soak mine in the sink (I have a big one) or in the bathtub with dish soap and ammonia and set soak (cover with a big trash bag to contain odor) for a couple of hours and use a 'brillo " pad to scrub clean. After the oven is all sparkly clean... try putting one of the aluminum oven liner trays in the bottom to catch future drips... they are easier to quick clean than the oven.. just be careful to not cover any of the vent holes that allow the heat to circulate.

Oh... there is usually a little "residue" after you self-clean... wipe it out with vinegar and water (after a spray on cleaner too) and let dry

Wipe out heavy spills first