I once wore a top with square neck line. In the US that was fine but here not so much. The lady was refusing to process my visa because of top and the agent i was with at the time kept apologizing on my behalf to her. She gave me the visa but i felt bad. Lesson learned....
the process by itself is not complicated. I would stay away from using an agent because that's what immigration looks for. When they see you used an agent they look at you differently and sometimes give you a harder time because they know you are willing to pay.