I've bought a cast iron skillet, pre-seasoned but am having trouble with things sticking when I cook.  

I haven't used detergents on it - it comes clean using a normal dish brush.

1) How much oil do you need to use when cooking? - I'm wondering if I'm not using enough..?
2)Does it mean it's pre-seasoning wasn't enough and I need to do it again?
3)Any other advice on what I'm doing wrong????

Yes  reseason it again and follow one of the procedures you can find on line. Cast iron is not magic it takes time for it to season. Mine are old and sometimes things still stick.

After you cook with it reoil it and store it with the lid on it. Never use soap to clean it. If it doesn't come clean with a brush and water use some salt as an abrasive. If it is beyond that put it in the oven on the self clean cycle, brush the ash out and then reseason. Grandmother used to throw hers in the fire place every so often instead. I still have one of her pans.

Foods may stick more if the heat isn't right when you put the food into the skillet as well...  A method to verify proper heat level is to watch the fat for evidence of slight rippling.  When you detect that, the heat is right to put the food into the skillet and the foods stick much less.

Another way is to put a couple of drops of water into the pan and watch for the water to "dance" across the skillet.

Because of the metal mass, cast iron typically takes longer to heat up, so people transitioning from stainless cookware aren't waiting long enough to allow proper heating.

All of the above.... and... I always put a small amount of olive oil, like a couple of drops in the pan and wipe around with a paper towel to coat the pan surface before I heat it  up - helps tremendously to prevent stickage.  

My mother used to sprinkle salt in her cast iron skillet, no oil, before frying burgers. I have no memory of how they turned out, but I surely would have complained if they were either burned or falling apart from having stuck. She was quite confident that "this is how it's done" with cast iron. Old school.

Quoted from ABJoe

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Because of the metal mass, cast iron typically takes longer to heat up, so people transitioning from stainless cookware aren't waiting long enough to allow proper heating.

Also, iron is not as thermally conductive as aluminum or copper, so you might have to set the heat a little higher.  There are occasions that I get a lot of sticking because I don't wait long enough for the pre-heat or because I dump a lot of cold, moist cooked rice all at once.

Quoted from ABJoe

Because of the metal mass, cast iron typically takes longer to heat up, so people transitioning from stainless cookware aren't waiting long enough to allow proper heating.

Hmm, think that could be part of my problem.  thanks for all the info, folks, will have a play this weekend.

NOTE:  All new (not old cast iron cookware) cast iron pans and skillets have a protective coating on them, which must be removed. American companies use a special food-safe wax; imports are covered with a water-soluble shellac. In either case, scrub the item with a stainless steel scouring pads (steel wool), using soap and the hottest tap water you can stand.


thought I would post that special note from link above, as it is so important!