If you haven't done so already, write down everything you already know. Start with your parents, and grandparents, and write down (or add to a family tree) what you know for sure. Then try to find your parents and grandparents in the census, starting with 1940 and working backwards. That way you will know where to look for family. Once you have census records, you can look for vital records, such as the marriage and births of your parents. Remember though, not all records are on Ancestry, especially more recent births and deaths.
Also, try different ways of searching. Names in records were sometimes mispelled, or the writing was so bad, that they were indexed wrong on Ancestry. So, for example, if you are looking for John Harmon in a census record, try looking for just Harmon with no first name, but add a county, state, or birthdate. If you know the county they lived in, you could even search on just a first name.
There are sites other than Ancestry that have good information as well. www.familysearch.org
has many census and vital records online, and it is free. Also try USGenweb at http://usgenweb.org/
Just pick the state you want, then the county.
Try googling the name, especially if it is not too common, such as "john harmon" Seattle Often you can find genealogy information that way.
If you want, you could also give us an example of something you are looking for - there are lots of volunteers who would be glad to help get you started.