My quick take -
Regardless of lenses, photography is about capturing light. So, the single most important step is understanding exposure and how it works. Once you understand the concepts of exposure you can start to evaluate how challenges a given situation will present to obtaining proper exposure. Then, given your lenses you can figure out where they fall short for a given situation. For instance, you may be shooting indoors in low light and your max lense speed is f5.6 - probably too 'slow' to capture good photos. You can compensate by using higher ISO and/or flash.
That first part will allow you to take the best picture possible under current conditions. The next part, in my opinion, is using post processing (like photoshop) to correct problems brought about from the capture - e.g. noise reduction because you had to shoot at high ISO, techniques for compensating for distortion or whatever. One of the benefits with digital is you have a great amount of things you can do with software to correct an image. But, having a good understanding of exposure will allow you to capture a better starting point.
All of which will help with the technical aspects - the other part is the 'art' of photography - capturing something of interest. That's where books on composition, etc. will help. THis is the area that I struggle with the most. I've gotten better over the past few years with the technical nature but am still struggling with the art side - and actually capturing something worth people looking at.
In both cases - technical and art practice is always the best approach.