What happens is that when certain negatives give you good prints from an enlarger or a contact, and others don't, you look for the differences to see why. You start understanding the reference points. Having no enlarger or prints to reference means having no clue or way to even figure that out. (I will address scanning in a moment.)
When I first started developing film I had the same want as you, so I adjusted blind and I got prettier looking negatives, more like slides. Later, when I did start printing I found I had made my life tougher with the adjustments I had made.
In your case, where you appear to be sending them out for scanning, you will find that there will be a significant range of exposure and development possibilities that the scanning system will allow.
That system, both the people and the software, very normally will take whatever you give them and adapt/adjust without telling you. The system may not give you the feedback you need to expose or develop better. To get the info you need you will need to talk with them and learn to ask the right questions of those who scan your work.
This may take some experimentation with you providing test rolls with more or less exposure and more or less development so that you can find your limits and sweet spots.
Adding extra development for your next roll, say the next step up on the instruction sheet, probably won't hurt, the system will probably just deal with it. If one scan is better than the other you will need to ask them why and see if they can fix the bad one before you can understand.