Mount & Blade: Warband

If you choose to make your own faction just conquer 5 places and give them all to yourself. If fighting for a faction make sure the leader likes you and after conquering a place ask the leader to give it to you. Unless they hate you you'll almost always get it given to you. You'll hit 5 pretty fast if you keep conquering and asking for the castles. Don't refuse any castle or village or the leader of your faction will be insulted and start rewarding you less fiefs.