In the midst of writing the post, I decided to double-check one of my "hints" and it yielded big results. Not yet another branch of long-gone ancestors, but this time a living sister of my mother that everyone suspected existed, a child nobody knew the name of. She was on the Internet wanting to find out what kind of person her father was, but was misspelling his very distinctive name by one letter. He died when she was four, back in 1970.
That was one hint: Google common misspellings of your ancestors' names in quotation marks.
By Googling (in quotes) the names of all of my great-grandparents born in the United States, I found that in every case, way-distant relatives had already done the genealogy going back sometimes hundreds of years. It didn't work when I typed in my grandparents' names, only my great-grandparents.
Another hint on Googling your ancestors is to Google them by their initials. I learned from the 100 year old news that a fellow named "Arthur Samuel Preston" is as often as not referred to in print as "Mr. A. S. Preston." Names are often abbreviated, too. " George Philip Sharp" is "Geo. P. Sharp", Jonathan is Jno., Thomas is Thos., etc. Make sure and Google "J. Thos. Caldwell" as well as "J. T. Caldwell" and "Jas. T. Caldwell" along with any geographical information you know.
Also, try Googling your ancestors last name first ("Preston, Arthur S.").
Millions of researchers have uploaded their genealogy databases into RootsWeb's World Connect project. Search for the names of all of your grandparents and great-grandparents here.
You'll see the three entries above for "Arthur Samuel Preston" bearing basically identical information. That means he's turned up in the GedCom (genealogy software) databases of three different WorldConnect users. Make sure and click on all of the links, even if it looks like it will hold the same information. Then just keep following the Father and the Mother back in time.
Some researchers' databases go much further back than others. Sometimes you'll have twenty different entries for the same ancestor, but check them all, especially if you get stuck. If you get to a complete dead end, just do a new World Connect search on the last ancestor where it leaves off. Chances are, that ancestor will turn up in several other users' GedComs. Notice, too, the different spelling of Preston's father's name in one of those entries. Run all the various and possible spellings through RootsWeb, especially once you've got dates and locations, and Google 'em, too!
Pretty soon the number of names of ancestors will become daunting. When I started, I think I knew the names of seven of my eight great-grandparents and that was it. Now I have hundreds of named ancestors, with a potential for thousands if I get back to spending lots of time on it.
To keep track of them all, I'm using the free, amazing, and excellent Family Tree Builder software from MyHeritage.com.
Here's another hint: Google Books. Google has scanned and made available the texts of millions of obscure local histories, and I have found extremely valuable information about many ancestors therein. Searching by initials works very well here, too.
Ancestry.com is probably the most valuable resource for genealogy researchers on the Internet, but I've found that doing the legwork on Rootsweb and Google helps me to make the most of Ancestry's databases (and their 2-week free trial if you don't want to become a paid subsriber).
Ellis Island immigration records are available free online. If your ancestor had a "funny foreign name" like some of my people, it was likely spelled phonetically by the immigration clerk working the door to the land where the streets were paved with gold, so take advantage of their "alternate spellings" and "sounds like" searches.
A place with a lot of free census records is http://www.us-census.org/. They are done in text, but if you do a Ctrl-F to search for the names it makes it very easy to find them.