Once you have gone through the records you already have, it is time to start contacting family members for more information.
In order to get better results, you should visit relatives in person. You should invest in a recording device, to tape the interview, so then you could just ask your questions, and let the conversation flow from there. Once you get home, you should transcribe the interview as soon as possible.
When transcribing the interview, include the date of the interview, the name of the person being interviewed, and the person conducting the interview (your name). If using a tape, you should also attach a label with these details to the tape. For a digital file, you would save the file with the date of the interview and the person being interviewed (2014-06-01 Interview with Uncle Bob). I use the reverse date format, so that the files can be sorted by date.
There are many sites on the internet that set out the types of questions you could ask your relatives. These are the 1st three listed on google.
If you prefer to contact relatives by mail or email, because of distance or family commitments, these questions can be incorporated into a letter.
If your relatives have documents relating to the family, you could ask to borrow the items to have them scanned or photocopied, or alternatively you could take a photo of the items, or make a transcription from the documents.