Make a big difference using a HDRI (High Dynamic Range Imaging).
Short brief about HDRI:
A HDRI is a SET OF TECHNIQUES used in imaging and photography to reproduce a greater dynamic range of luminosity.The HDRI images has different exposure values. The non-HDR images have limited exposure range, resulting in the loss of detail in bright or dark areas. HDR compensates for this loss of detail by capturing multiple photographs at different exposure levels and then combine them.
About realistic texturing u can find a tutorial by Andrew Price here: https://www.youtube.com/watch?v=W07H7xeUnGE
s the best. He will teach you some secrets of photorealistic texturing. He uses CrazyBump (for creating normal maps textures and specular) and them put in Blender nodes. Note: Its very important do make the final render in GIMP or photoshop by changing colour tones, adding cracks, leaking on walls, shadows, even if you want to add human silhouettes in your scene (this is best for architectural visualization renderings)
There are multiple ways of lightning your scene (using a HDRI, using a sun lamp). This is according to your scene. For example in interior redering you better use the sun lamp with ambient oclussion checked and for outdoor scenes you can use HDRI light.
Here is a basic tutorial using HDRI lightning in Blender: https://www.youtube.com/watch?v=kBRP5sPsDfI
Just google it for more tutorials and you`ll find plenty of it. Have fun!
Hope this was useful.