How to efficiently identify Lego bricks and find their names?
In my experience, the Bricklink catalog is the most complete parts list. It is organized in fairly logical tree by part type (brick, plate, wheels, slope, etc). Once you get familiar with it, you should be able to identify parts fairly quickly.

If you take a look at the 2 parts that you mentioned in your example on Bricklink, you can clearly see the difference between them:

3004:



3004px3: