My dad died when I was a child and I know nothing about his side of the family how do I find out more?

His obituary, in old newspapers on microfilm at the library, would tell you about him. It might list his parents. It will almost certainly list his siblings, wife and children.

My dad died when I was one year old and that was 71 years ago, so most of his siblings are gone by now. I have photos of him, but that's about it.

Same here.  I asked old folks who grew up with them..You can also make a visit to the museum run by the County they lived in.   Tons of old newspapers, letters, pictures, etc.

You will need to start with getting dad's birth certificate. That will give his parents. Then take it from there via Ancestry.com or similar

Try Family Search or Ancestry.com to research your father's family.

I had the same problem.  Plus mother really shared little.  I knew he had lived in San Francisco, and started from there.  Newspaper articles gave his parents' names, job, learned he had an uncle elected to state assembly and murdered during a hold up of his saloon.  Found one set of his grandparents immigrated from Ireland in 1871, while the other side went back to 1620.

Newspaper articles can be a great help, but require some deep digging to find.  Church records can be a big help if you know where to go (having that murder helped, since the entire family used the same church).  Learned when/where he went to college, but they never responded to my queries despite offer to pay.

Have someone buy a 23& ME KIT FOR YOU $199.00- DO YOUR DNA AND GET HEALTH INFORMATION AS WELL.

Start with getting a copy of his death certificate. Then get his birth certificate and his SS5.

The same with his parents. When you get back before 1940, you can look people up on the US census.

Try submitting saliva to Ancestry DNA. If anyone on your dad's side of family has their DNA there they will let you know. You could also look up his past friends or neighbors to question them.

Your mother is your source of information she could still have his records, such as their marriage certificate which will give you information like his job, his parents names, she may have his birth certificate too which will confirm that information, if not you will need to purchase a copy of the marriage cert and birth cert and that will give you a start and three generation tree which is proved... from that you have his parents names, so can start researching them and so on