Have you played Plants vs Zombies (PvZ)? Its the wow version of that.
Probably haven't, if you're asking, so I guess I should put it this way because PvZ (or in this case, PvG) is a time management tower defense type game, here are some tips:
-Pretty much, plant an attack plant with you see a ghoul in the row.
-Start planting at the far end (left) and avoid planting things at the right if possible.
-Use emergency plants (the vines and the stones, also pumpkins later) only when you are in your 'where is my OMG button?!' stage of things.
-Plant sun generators when you have extra sun and no lane empty of attack plants.
Madoran (Horde-US): Eclectic, Tauren Guardian Druid.
Fenris (Horde-US) 'Main': Miach, Undead Holy/Shadow Priest.