We commence this list starting with the most annoying mistake: Don’t auto-attack the creeps! Now, this may seem counter intuitive, but the idea is to always aim for the last hit only! Just get the gold and stay in the same position. Don’t push! (That means going on the offensive) Do this so you can farm up quickly and get some valuable XP (“Farm” means getting XP and gold through creep last-hitting).
One of the critical mistakes new players often make is to push too hard early game! They often go near the enemy tower and then retreat with low health. Sounds familiar? The only thing this so-called strategy does is to give the enemy some free farm. Not only this, but it also allows an enemy hero to flank you from behind and get an easy kill. Since you are so far from the safety of your tower, you will probably die very quickly. Another important concept is denying creeps. What you do is manually press the attack button and kill your own creeps when they are about to die. “Why would I kill my own creeps?! They are my friends!!” you may ask. A simple reason is that, when you deny them, you do two things: you take away your enemy’s chance to last hit while getting the bonus gold. And you deny him some XP. It has more pros than cons.