One question was what to do with a Gedcom file you receive in your e-mail from a cousin so you can share genealogy family tree information. The first word of advice was not to merge anyone else's family tree with yours, but see what the other family tree has, look for the information with sources, and use that to continue your own research.
As might happen, a blogging "expert" on Family Tree Maker software, Russel Worthington, posted a series of how he opened a gedcom he received from a friend and created a separate tree for it in Family Tree Maker 2012. Russ gives great instruction and visuals on how he goes about doing different things in Family Tree Maker. The link to his seven consecutive posts about the Gedcom is at his blog: "FamilyTreeMakerUser" at
I recommend that users of Family Tree Maker subscribe (free) to his site you you can benefit from the great information Russell figures out.
Another terrific blogger who does research on using Family Tree Maker and Legacy is Randy Seaver. His blog is at http://www.geneamusings.com/ Randy comments on the use of the gedcom and Russel's advice, in one post on the Nov 25th posting.
Family Tree Maker 2012 - where to start a new separate tree