1. 1900
The siblings were not born in 1880, so that census would do no good and by 1910, they were probably not living with their parents. The 1890 census was 99% destroyed and for all practical purposes, does not exist. Learning what is available on each census is a basic bit of knowledge for genealogists.
2. International Genealogical Index
The IGI is the world's largest genealogical database with births and marriages of over 300 million people worldwide. What makes it so valuable is that it is derived from primary sources. Information from the birth/marriage records of many U.S. counties and European churches has been extracted to the IGI. It also contains unverified information sent in by individuals, but you can easily tell which is extracted and which is submitted. This information is available free of charge at any LDS Family History Center as well as many public libraries.
The Mormons (Latter Day Saints) are interested in genealogy for religious reasons but you don't have to be Mormon to take advantage of their work. They have amassed an incredible collection of records from all over the world. These records are on one and a half million rolls of microfilm and are housed in a giant library in Salt Lake City. If you can't get to Salt Lake, they maintain branch libraries known as Family History Centers where you can rent the microfilms for a few dollars each. I can't imagine doing genealogy without using this resource.
3. Grandma
Grandma and the rest of your older relatives should be where you start. The biggest regret family historians voice is that they didn't ask questions when they could. Since you always start from what you know and work back from there, you'll take what you learn from Grandma to make family group sheets and pedigree charts.
Next, you'll probably want to write to the county courthouses to get vital records (birth, marriage, death) of all the people on your pedigree chart. The National Archives, home of the census and important immigration and military information, is probably your next stop. Then you'll want to explore all the goodies at the Mormon library and on the Internet.
4. Determine where the town is located and how boundaries have changed over time
Whether you are searching in Elk Garden, Virginia or Vörstetten, Germany, knowing the location is vital to being able to do your research. And not only do you need to know where a place is now, you need to know where it was when your ancestors were there. Since for the US, the county is the keeper of many of the records, knowing how county boundaries have changed tells you where to look for the records of your ancestors.
Other parts of the world have their own "genealogy of place." German records, for example are mostly kept at the local level. Kingdoms, duchies, and states all changed boundaries over time.
Having names and dates without places is useless and does not tell you anything about the lives of your ancestors. Whenever I see a "genealogy" on the Internet with just names and dates, I click the Back button. The people listed may be related but I have no way of knowing.
5. Died without a will
Before you spend your time and money climbing your family tree, learn the terms used by genealogists so that you can communicate with others. Find a book at your local library or a site on the Internet that discusses the principles of genealogy and these basics concepts:

Standard forms and conventions
Primary vs. secondary evidence
Documenting sources
Record groups: census, vital, military, church, probate, land, immigration

How to construct a query

6. First cousin once removed
Relationships are what families are made of, so be sure you know the terms used to define a family. And don't think a fifth cousin is too distant to care about -- you'll want to know all the branches of your family and you'll meet many of them online.
7. 8 May 1904
Always use a 4-digit year -- the year 2000 problem is nothing new to genealogists! Put the day before the month, as they do in most countries. Spelling out the month helps avoid confusion.

There are conventions and standards used by genealogist. Learn how names, dates, and places -- the basic building blocks of genealogy -- are written before you start entering the information on charts or in your computer.
8. None of the above
Always use a woman's maiden name. If you don't know a person's name, don't substitute another one.
Some other name and place conventions are:
Do not use titles such as Mrs., Dr., Jr., III, or Esq. in a person's name. They are relative terms and not part of their name.
Write US places as city, county, state. Since the county is vital to doing US genealogy, don't leave it out. Look it up if you don't know it. There are standard conventions for other countries as well.
9. 1 - 2 - 3- 4
The baptismal record, recorded at the time the event occurred in the most reliable. In general, the closer the record to the event, the more reliable. Another consideration is who supplied the information. The census information was probably given by a parent but could have been given by a neighbor or a child. Keep in mind that if it had been the 1840 census instead of the 1850, no names other than for the head of household are given and other family members are just "hash marks" under sex/age range columns. Information on a death record is usually filled in by someone who was not present at the birth and so birth information is second-hand information. Unless the family history book includes sources, the information in it can be considered merely clues for you to research. Same for undocumented information you find on the Internet.
10. False
Surnames were used long before they were commonly recorded. You will probably not be able to trace back to when surnames were first used. (There are some exceptions, for example the early Dutch in America.) So how your ancestors got the name will not help you find them.

Before this century, spelling was not important, most people could not write, and foreign names were mangled or contorted. Over the many years since your ancestors first started using a surname, it could have changed in ways you could not know. For these reasons, saying something like, "Our Elliotts have always spelled it with two L's and two T's" may mean you'll miss some important clues.

And don't forget that the surname you have is not the surname of all your ancestors. It is, in fact, your least reliable line, but often the one pursued most vigorously by men (yes, men) who are newcomers to genealogy.