First gather all information you have on the person you are trying to locate. Name, Date of Birth (DOB), Place of Birth, Newspaper Articles, Documents, Photographs, etc. Make a file on the person you are attempting to locate.

Here is an example of the documents you might use:
Family History Worksheet
Resource Record

Now that you have your file. Look at the information you gathered. Siblings names, cousins, relatives, dates, locations, etc. and also consider where you gathered the information from. Sometimes family history when retold might be slightly wrong or skewed.

ADOPTED:
Oregon is adoption records are avalible please check out this site for more information.
Also register at the online registries on the internet.

Now try these tips for more information:
A couple of things I would start off by pursuing would be :
 BORN BEFORE 1930 - Check Cenus Records for Siblings & other information.

1. City directories / Phonebooks are ofter stored at local genealogy or regular libraries
2. Marriage records can be searched at local courthouses if you have a county. Some of this type of information is avalible online : such as Vital Search    &   Genwed 
3. Checking for any criminal / civil activities at the county courthouse, such as traffic tickets provide more information. Some things may be expunged after such a long period of time has passed
4. Locating the owners / managers of the property resided at during the time period and seeing if they maintained records at the county courthouse or check for an assessor page online.
5. Voter records from this time period, if maintained at county courthouse or online.
6. Local Library may have computerized newspaper indexes, search by name for stories.
   
7. Some states have online birth / death / marriage records
   

                      DEATH INDEXES                 VITAL SEARCH               GENWED