There are three basic styles of modeling of which I am aware. You should choose to study the one most pertinent to your field of work: entity modeling, object modeling, data vault modeling. I prefer entity modeling for corporate work. Object modeling is used for many "standards body" work, specifically HL7 healthcare for my field. I find data vault modeling of very limited use.
With in entity modeling there is "normalized" vs. "dimensional".
I began learning by reading Bill Inmon, Ralph Kimball, and Len Silverston. I advanced my training by reading models created by experienced people here at Teradata.
I know a few places to get started...
Len Silverston has lots of good information including videos on Youtube and at http://www.univdata.com/
I like the intro material by Missy Wittmann at:
Once you have a good handle on 3NF (Third Normal Form) modeling then looking up Ralph Kimball for dimensional modeling. That is another step in modeling which creates reporting models for end user access.