So I started playing Crusader Kings I, and thought I'd start as a count and work my way up. Cornwall was my first choice (since it was the first count title in the list that I was familiar with in terms of geographic location). I'm now running into the problem that I don't seem to be able to wage war against any of my fellow Englishmen without the King of England booting me out of the kingdom and then coming down on my head like a ton of bricks.

My question is this: Is it possible in this game, by some combination of schmoozing, gifts, and marriages, to make yourself such a favorite of the king that he won't interfere in your rivalries with other counts or am I pretty much restricted to waging war against non-English nobles?

The manual said it was a bad idea to attack fellow members of your realm, but I don't know if "bad idea" means "generally try and avoid this" or if it means "this is completely impossible".

Well, in my first game of CK1 ever, I have started of as a Count of Gemer (it is a place in my country and I live nearby), then I have become Duke of Nitra, and now I am King of Hungary. The thing is, I did so without attacking any of my neighbours. I have just slowly raised my children and married them to the right people. Once in a while, I had to resort to some assassinations and so on. I think it took me only 3 generations to became the King of Hungary that way.

This game is really more about relationships than wars. With patience you can achieve much more than with direct assault :)

Oh and of course it is not completely impossible to attack other counts within the same realm, but you have to cherry pick your opponents, because most of the time, the King of your realm has almost always much bigger army, than a small Duke or Count. If your opponent is Heretic or Excommunicated, you have also chance, that your King will not interfere as far as I know. Most important is to have valid claim on the county and probably have your realm very close to the 2st place of possible inheritance.