Asking questions from Professors

There are thousands of doubts, numerous insecurities for a student to get his best output from a university experience. It is very critical to understand the education model and the strategy. I have always been confused and bewildered by the right strategy. When we take a class under a particular professor, the first thing which is in our mind at the top is to get the best grade and hence keep a good impression on the prof. Then we personally assess the professor as a person and then rate him whether he is approachable, whether you can ask questions to him what you want to and whether he would be able to give you the key answers to what u are looking for.
But still the important point is to not just keep thinking/deciding and approaching the professor. He may not be able to revert with the precise answer but he would greatly benefit you in clearing your doubts and relieving u off your anxieties.
I have till now interacted with 8 professors and everyone in one or the other way has influenced me and impressed me with his knowledge, his attitude and some have disappointed on certain aspects I had expectations as a student.
Now the question and the reason comes to me how well I was able to channel the professor's work to my benefit, to learn and to grasp the topic. Definitely, homework is crucial and method to find your way out of the jargon.
I put up these questions to myself? How will did I utilize my university experience?
Did I give it my best shot in taking control of my subject?
Did I put up questions properly to the instructor?
In what way did I communicate with the instructor, was it only on my personal internal way, or did I also make the professor notice my thirst to gain knowledge.
Then I get baffled, who all should I contact.
Prof Leahy who taught me DSP in 1st sem, who had been marvellous in his job but I got a poor grade. What questions can I put up to him now which he can answer back. I decided to revert back to Networks as I found DSP too mathematical, and multimedia also interested me. Somehow I could relate to VOIP through this. I have been looking for convergence, where I can learn both aspects of telecom and networking.
Then the second prof I am highly influenced by is Crowley. His style of teaching and his attitude is amazing. He is very genuine, lively and puts in his soul in teaching.
Then prof Havaldar, who taught me something I was looking for as a course, multimedia. It makes the most meaning for VOIP where you can relate the two disciplines together.