To answer your question, it''s really about personal preference. I recommend going to the top of this page and looking under the knowledge section for the "Basic 4c;s".
That should explain things for you well.
Some people are very color sensitive and prefer to stay at the top of the color chart, others like it when their stones show a hint of warmth.
Similarly, some people prefer that their stones have little to no inclusions, whereas others just prefer that the stone is "eye-clean" (no inclusions visible to the naked eye).
I suggest you take a look around this site to compare and contrast all types of diamonds.
I''ll add to lucky''s great advice, to check out this video on color. It would also help to see some stones in person. The better the cut, the less color/warmth will show. Seeing some Hearts on Fire would be a good thing too. (not to buy, just to look!)