If one of my friends was entirely new to demigod or gaming in general, and I had to give them one rule to live by and become a better player it would be:
If you are dead you did something wrong.
There are a million ways you can end up dead. Either you went too far from base, other players, didn't have enough hp/speed, your heal got interrupted. Maybe you just weren't watching the other demigods close enough and you got ambushed. Death is the way or the opposing team telling you "you are not allowed to do that, now here is your penalty".
If you happen to be a noob (nothing wrong with playing casually), but you want to become a better player all you have to do is learn from your deaths. Congradulations, you are now an intermediate player.
Now lets say you know how far you can travel away from base and still make it back in time to survive and all those little things that come into play just to stay alive. Not dying is not enough to win a pro game. The problem is that there is no clear feedback mechanism like dying to tell you exactly why you started losing. Often times you will slowly fall behind until you find youself unable to fight back at which point the game is already over, even if they haven't got near your citadel.
In an extreme example, lets consider a regulus who never leaves the heatlh crystal and just continually snipes people and towers without ever putting himself in risk. Most likely he will get a few kills, destroy a few towers, and the citadel will crumble right in front of him 30 minutes later without him dying once. Its obvious this is a horrible strategy, but it follows the above rule perfectly.
If you are not in danger of dying, you are doing something wrong.
When I say this, I do not mean you should be putting yourself needlessly in danger or that you should be putting yourself in situations where you will certainly die if the opposing team plays properly. Instead I mean to say that you should be aggressive enough that you maximize the pressure on the other team. The regulus I mentioned before obviously contradicts this rule, but how about situations that actually may arise in a pro game?
Say your teammate in running from two demigods and you just arrive on the scene. You know you can't fight them 2v1 so you stay back near a tower and once they get into range you pop off a couple shot from the towers safety to make them retreat back to the flag.
Or, you charge ahead knowing that they will be after your teammate and shoot them all the while they are chasing. If they focus you instead you can always run but they still think they can kill your teammate. In the end you damage one of them enough to force them back to their crystal and are able to take the remaining demigod solo, forcing him to retreat as well and capping the flag for yourself.
As a second example, suppose you play rook and are holding a lane while the other team is fighting your teammates 3v2. You can't get over there to help them, but you can't kill the tower in your lane without taking massive damage since your build doesn't have structural transfer. However you have the health to spare, so you autoattack the tower until it blows up leaving you at half health, but by the time the enemy can take advantage of it the passive regen has taken you up to fighting strength again.
Really though, there are a million different subtle situations that can slowly win the game if you are aggresive enough to take advantage of them. Pro games can become very complex and interesting as each side pushes things to the limits, even to the point of dying yourself to kill two of the enemy demigods.
Hopefully, this post will open up new tactics to intermediate players out there looking to get more of an edge on their opponents. ^^