If you have a non-kosher food utensil, kasher it before you immerse it in a mikva (tevila).
 

You may kasher oven racks by putting them in a self-cleaning oven and running the self-clean cycle. Or, clean with oven cleaner and then put into a normal oven on its highest temperature for 40 minutes.

To kasher a gas stove:

• Remove the burner grates,
• Clean off any deposits,
• Place the grates on a clean surface inside the oven, and
• Heat the grates to the oven's maximum temperature for 40 minutes.

 

To kasher an oven for Passover:

• Clean it completely, including any hard deposits, and
• Heat the oven for 40 minutes at its highest temperature.

To kasher a clean electric stove, turn the burners on to the highest setting until the burner glows red (this is easier to see at night) or until a piece of paper will burn on it (the paper does not need to burst into flame).
 

To kasher an oven that is not self-cleaning, you must:

• Remove any deposits on the walls, racks, and window.
  Note If there are stains or deposits, you must clean them off or burn them off. If the stains or deposits do not come off after two cycles of using strong oven cleaner such as Easy Off, the oven is considered sufficiently clean.
• Turn the oven on to its maximum temperature for 40 minutes.
  Note Self-cleaning ovens attain a higher maximum temperature than do non-self-cleaning ovens.

To kasher a self-cleaning electric or gas oven, you do not need to clean it first. Just run the self-clean cycle.

Make a grill red hot to kasher it.

You may not kasher a dishwasher (even if it is stainless steel) from dairy to meat, or vice versa, in order to use the dishwasher for dairy and for meat utensils, even sequentially.

When kashering an oven or utensils for Passover, you may kasher:

• By Libun

• By Hag'ala

 

Since microwave oven walls and doors do not normally get hot (more than 120° F, or 49° C), there is usually no need to kasher them from milk to meat (or back to milk); from ordinary use to Passover use; or from non-kosher to kosher. Just clean all surfaces.

You may not use a non-kosher cooking utensil (pot, pan, baking dish, etc.) for cooking even if the utensil is clean and has not been used for more than 24 hours (unless you kasher it first).

Situation Kitniyot were cooked in a Passover utensil. 
Situation 1 The kitniyot's volume was less than 50\% of the volume of food cooked in that utensil. 
Status The food may be eaten and the utensil may be used on Passover (no need to kasher). 


Situation 2 The kitniyot's volume was more than 50\% of the volume of the food cooked in that utensil.
Status The food is not permitted to be eaten. 


Situation 2a The kitniyot's volume was more than 50\% of the volume of the food cooked in that utensil, and the total volume of the food cooked (kitniyot + non-kitniyot) was less than the normal volume of food which is cooked in that utensil.
Status The utensil may be used even without kashering, as long as you wait at least 24 hours after the utensil has been cleaned. 


Situation 2b The kitniyot's volume was more than 50\% of the volume of the utensil itself and more than 50\% of the normal volume of food cooked in it.
Status You may not eat the food (until after Passover) and must kasher the utensil after waiting 24 hours. 
NOTE You may only kasher a utensil on chol ha'moed but NOT on the festival days themselves. 

Do not cook or eat meat-containing and fish-containing foods together:

• After eating fish, you must eat and drink some other food before eating meat-containing food.
• After eating meat-containing food, you must eat and drink some other food before eating fish.