GEDmatch, a DNA tools site, was originally created to compare GEDCOMs, a function you can still use it for. A GEDCOM is a plain text file of your family tree formatted so that any genealogy program can understand it. Click here for the wikipedia entry explaining this in more detail.
In my talk I emphasized that it is best to upload a privatized GEDCOM with no more than 10 generations of ancestors then connect it to the DNA test for that person. This will help you use the relative matching tools. I promised in the presentation to explain how to create a GEDCOM. So here are a few of the many ways.
Did you know that there are chrome add-ons that can collect pedigree trees from many genealogy sites and DNA testing sites? These tools can collect a tree of ancestors as an ahnentafel list which is a very useful and compact format to scan for common ancestors and locations.
When it is just a few new relatives at Ancestry, you don’t need those add-ons. After all, it is easy to use the Tools menu on the Profile Page of the ancestor you want from a tree at Ancestry.com to copy over a few people. In fact, if you copy one person over, you can click back to the original tree and copy them again in order to get their whole family group, just like in an Ancestry hint. I do recommend that you check sources and make sure that this is good information. Even if you are making a Quick & Dirty tree (Q&D) for an adoptee, it is best to check it over, as some trees on Ancestry.com are quite unrealistic with parents born after their children and other such errors.