How to open a rusty nut?

I bought a second-hand bicycle a couple of months ago and now I got a flat tire. I can't take off the wheel to change the inner tube because the two nuts that are holding the wheel from both sides are quite rusty. What should I do? What can I use to get rid of the rust?How to open a rusty nut?
WD40 and heat. You don't have to go to the extreme of heating to red hot. That will damage the parts. After repeated applications of WD40 over a couple of days, boil a kettle and pour it whilst boiling over the rusted nuts. The sudden expansion created should loosen the rust. Use the correct size hexagon socket or ring spanner on the outer nut and it should turn. Tap the spanner lightly with a hammer too as this will tend to shock it off. Repeat the process if necessary.How to open a rusty nut?
Diesel is best beats WD 40 any day it eats in to rust you might have to put it on several time in a day and then give it a go.
Don't use a regular spanner is this is likely to shear the nut. Get some rust eater or try to gently ease it by fully oiling it and using a socket set.
there is a very thin oil 'eezit' just for this job squirt on and leave for a day. alternatively lever the tyre off find the puncture by pumping air in, mend it and replace the tyre. That's easy.
Give them a little squirt of liquid wrench. You can also patch your inner tube without removing wheel from bike! DO NOT use a torch as bike components are heat treated and you may soften a part and get hurt in the future!!!

Mark
if all the oil suggestions don't work, use a gas powered torch, heat the nut up till it is almost glowing hot then spin the nut right off, this works Every time
wire brush the rust off, then apply duck oil, leave it overnight apply some more and attempt to move the nuts!!
try a little WD40 %26amp; leave it to soak for a while....then get your spanner on it! WD40 works wonders....it really does!!



edit: oops!! didn't see other answers....first answer is correct from Ross!!
put a blow torch on nut to heat it up
spray WD40 on it that should do it,
put oil on it?