Summarize this article:

Populate your tree with all of the current information you have compiled.  As you fill out and populate your family tree make note of what resources you are using. When you have populated your tree, go over all your resources and see if you missed something. Then, you may want to locate all the information, pictures, files, etc. you didn't use. Separate the unnecessary information from the necessary information. You can do this in a chart you've already created or make a new one if it's easier. But you should now make note of what information you are still missing.  Check to see if you have all the information you want for each family member. Are you missing birthdates, marriages, or any other relevant information? Make detailed notes of what you still need. Perhaps you couldn't find any information on who your great-grandmother married. Or, you still don't know when your grandfather came to your country. Start searching again, this time being more specific as you know what information you need. Try searching through records using different names or dates.  Depending on when a certain family member moved to a new country, these members may have had a different name. Alternatively, you may eventually discover that the dates you thought were correct were actually wrong. Ask your family if anyone had a different name or a variation of a name. Search Google and other records with different parameters. You can set date ranges when searching on Google to filter out any dates you don't want results from. Now that you've started your family tree you can continue to expand it and fill in all the blanks as you discover more.  When you find new information, add it to your tree and notate where you found the information. You can continue building out a record of your genealogy going as far back as you wish.
Continue to fill out your tree. Create a chart for the gaps in your tree. Search for different variations of surnames. Continue adding information as you find it.