OK, I have found and understood all of the rules about which resonance form of a molecule is most stable APART from assymetrical allyls.
I've got a molecule;
two methyl groups on one side of double bond and a single carbon on the other side (with the +ve charge):
which resonates to having the positive charge near the methyl groups, a single bond and then the double bond furthest away from the methyl groups:
WHICH one is the most stable?
I hazard a guess at saying the one with the positive charge furthest away from the Methyl groups because there is more positive charge in that general area already, but then confused myself by thinking ... other stuff.
Thanks for any help, this is revision for an exam on Wednesday and although I've confirmed and understand a lot of stuff, this simple thing is doing my head in!