This is where I'm keeping thoughts for an Ancestry users WeRelate page.
Importing a GEDCOM from Ancestry
Start with a small GEDCOM! If you have a large Ancestry user tree, consider importing it into an off-line genealogy software (like Family Tree Maker [Brenda - Test a free software] where you can reexport a smaller portion of the tree before adding it to WeRelate.
Alternately, take advantage of the import features in We Relate to select a "root person" to your we relate tree and then add only names that relate to that person for a few generations (less than 10, and the fewer you import, the easier time you will have with your first tree).
Each time I imported the GEDCOM, I'd select one of my grandparents to be the root person, and then import only those people related within some number of generations from that root person.
Ancestry data issues to be aware of
At Ancestry, you may enter a date as (for example) "After 1805," but when it is imported by others via a Public Member Tree, the system turns your speculation into a specific year: 1805.
At Ancestry, copying information from "Your" tree to "My" Tree can lead to a sort of circular reinforcement of data -- i.e. I have often found information on Public Member Trees where the source is other public member trees, one of which turns out to be my Public Member tree. So I haven't actually shown that Betsy Spaulding married Daniel Blaisdell in 1805 by citing a Public Member tree; instead, I've just shown that some other people copied my original speculation that Betsy Spaulding married Daniel sometime after 1805.
Almost all of your sources are going to import as Ancestry being the author. For Census records, assuming your ancestors lived in more than one county, you'll have to update these sources by hand. For other sources that are public records or seem likely to already be sources in WeRelate (example: Social Security Death Index) right-click in the Matched Page field and go to find/add matching source
Now that you're here
Keeping track of YOUR tree and finding relatives