The first thing you need to know is that the goal is to gain six Dragon Runes and not to crush your buddies that are across the table from you. If you focus all your energy on military conquests, you will feel good inside when you view your massive territory, however, you will lose. The game is more about questing and bidding then marching plastic to the other side of the board.
That being said, initial position really matters. So if the board is shaped like a uneven triangle, try to avoid being in the short middle. The board really decides who will be attacked first. If you are at a disadvantage, try player orientated diplomacy to curtail the number of fronts you have to fight. But once again, this isn't too much of a worry since the war part of the game is more of defending territory so that you can put runes in it.
Questing is one of the main ways to get a Rune. Since a hero only quests during the summer, you only have six moves. Therefore, the more heroes you have on the board, the more quests you can complete and achieve more rewards. Some rewards can be traded in for Runes almost directly (spend some additional influence), but at worst case, you can trade three in for one rune with the Hero title card. Regardless, the more heroes on the board, the more chances you have to seize opportunities to gain runes.
An easy way to get a Rune is to complete your objective card as quickly as possible. If you do so, you may get a chance to get another objective card in the spring.
The real secret of the game is influence. The reason why you want resources and territory is not so much to build armies but to produce influence. Influence allows you to straight out buy a Dragon Rune during the winter sometimes. Always have some on hand and you will find opportunities to gain runes. Make sure you build the influence add on your stronghold.
Keep in mind you should always: