If you are not finding expected results, try searching different name spellings/variations (for example, La Sorda, Sorda, and Lasorda, or Francis and Frances) and date ranges.
Be prepared to search for different surnames. This is most common for maiden names, but can also occur for other reasons, such as adoption.
Begin with the nearest generation about which complete information exists and work back in time from that point; research one name or family at a time; focus on one locality where ancestors lived and identify it in terms of the jurisdictions to which it belongs (county, state, district, province, etc.).
Document your work as you progress.
As you learn more information, return to previous searches and supplement them with new data.
When possible look at an image of the original document, not just a transcription.