Depending on which country you fly check out VMF-251 as well. </shameless plug

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As has been said, there are some marginal differences between the 1C and 1D, but not so much that it should radically alter your flying style. I do find the Charlie to be somewhat less forgiving at low speeds.
I have to disagree with Ren on a couple points:
* Regarding fuel, take a full tank + 1 external for flights of at least a sector. The 1D, C and 4 have a limited endurance, especially in comparison to the 1 and 1A. The DT doesn't hurt as bad once you drop it since the pylons are permanently fix, but with the single fuel tank it's better to have too much just in case you're forced to engage early by a con halfway to your objective. If you get a fuel leak (which seems to nearly ALWAYS be the first thing damaged, especially in the -4

) it also gives you a little more time to get to a good gliding altitude before your tank runs dry.
* You'll get a lot of different viewpoints on the landing gear, but IMO the only time to use them in combat is for dive-bombing or if you're entering a fight from high altitude to prevent overshooting a low target. They bleed E too quickly and regardless of how well she handles at low speeds, you really want to keep your speed up in large fights.