To be honest the best contribution you can do to the game is beeing a player

. Play the game and play it online ( WAIT in the lobby and ask people there if they play with you!!!! )
Some important hints for new players:
Range units in background:Place a stable building in front ( indians totem for example ) and place your archers behind. Now your archers can shoot the enemies melee units which try to attack the totem.
Same thing works if you have melee units in front and archers in background.
Ideal is a setup like this( indians) :
melee units in front, axethrowers in second row and firearchers in background.
Fight evil units firstIf you are in a fight you should mange it! If there are very strong units in your range, like a thunderbird for example, better kill this unit first.
Imagine Indian attacks you you first want to kill thunderbirds, followed by horsemen, axethrowers, firearchers, because those units make a lot of damage to you.
Shoot standing units firstIf a fight starts archers typically try to attack the nearest units, which is typically runnning to you. But its hard to hit running units and you cannot do a lot of damage to them typically. So if possible, first try to shoot already standing/fighting units because they are easier to hit and you can do more damage to them.
Grouping:To control things like these you can make groups which are accessed by the keyboard numbers. To make a group, just select the units you want to put into a group. Then press ctrl-"1" to bind these units to the keyboards "1". To recall this group, just press "1". You can use keyboards 1 - 0 to make groups.
Attacking:Attacking with right mouse button doesn't work too well, in many cases. Better try to use the "a"- key.
Select a fighter ( or many fighters ) and then press "a". Now click to the ground on the map or on the minimap. Now your fighters will start to run in attack state to the given position, attacking everyone they see.
Of course you can also attack a unit directly this way. Just click a and then click the enemy units. even if you missed him, the unit will at least start to attack. Thats why advanced players nearly only attack this way!