This is a guide to my preferred start, which is almost always as a count or as a small duke in 1066. But if you start out as a vassal, your first goal will probably be to take over your liege's lands, so if that's not the direction which you want to go, an independent start might be better. Note that independent counts get a +50% bonus to their levies in their capital, while vassal counts do not get any bonus. In addition to the capital county bonus, independent dukes and above get a +25% bonus to levies in their holdings within the capital duchy. (For vassal dukes and kings, the bonuses are +25% for capital, and +15% for capital duchy).