Not sure what you are asking. There's no pushbutton answer to "realism", even more so with AE's extremely limited rendering options. Start by actually matching the direction of the main lighting to your sun and add more lights to emulate diffuse bounce light then tweak the parameters until it looks believable.
Okay. I have placed the text in the position that I wanted using tracking. Now I just want to change the look of the text to blend in well with rest of the environment. I tried adjusting shadows a bit but that didn't help much.