How to know the formula of different compounds?
In my experience if someone says something like tin chloride they are usually insinuating you know the most common oxidation state that metal is found in when complexed with the chloride atoms. This is a bad practice of them if they haven't explained further but I digress... In this example with the metal center of the complex being tin, the most common oxidation state is +2. This means the formula in its neutral state would be $\ce{Sn^{+2}}$ with 2 chlorides with a (-1) charge making the molecule neutral at $\ce{Sn(II)Cl2}$.

Different effects cause  common oxidation states for specific elements. These are outlined further with Mendeleev's Periodic Law. It breaks down into how shielded the nucleus is by electrons, and how big the radius of the atom is.

A further explanation of tin's common oxidation state calls upon knowledge of the inert pair effect, where elements to the right of the second and third row transition metals such as: In, Tl, Sn, Pb, Sb, Bi form compounds that are less reactive than one would think where the oxidation state is 2 less than the expected group. This is caused by the $\mathrm{ns^2}$ electrons being relatively inert. The cause of that nonreactive state is because of two reasons specifically:


Larger-than-normal effective
nuclear charges in these elements.
Lower bond energies in their compounds.


A good book to use referencing this subject further is Descriptive Inorganic, Coordination, and Solid-State Chemistry by Glen E. Rodgers. This is the book I own and used for when I studied periodic trends, and inorganic chemistry as an undergraduate. It's a great book for this subject, among others.

Also there are commonplace names that are used as somewhat of a slang for certain compounds used in research frequently. These can be learned through experience, or you can just google common names... All formal names are dictated by the rules set forth by the IUPAC. Learning those rules would be good idea. Also keep in mind that in some research projects you will encounter molecules that have informal nicknames too.