Hi @devfire Start from the known and work backwards to the unknown. Begin with living relatives, and collate as much information as you can re birth and marriage dates, and ask if they know of names and dates of death of deceased relations (do bear in mind though, that sometimes there are skeletons that people want to remain in the closet).
You can order birth, marriage and death certificates from the GRO (General Register Office) official website.
FreeBMD is a good search tool (use their reference number to order certificates as above), as are the censuses. Rather than pay for something like an Ancestry subscription, most libraries have access for free.
Collate all the information you find out - for instance a marriage certificate gives both names, marital status (ie if they were married previously), ages, address, occupations and details of fathers and their occupations. There will also be witnesses named on the certificate, and who are often related in some way.
Go by official records, not trees uploaded to databases by other people, as they may contain errors.
DNA research can be useful if you hit a brick wall, but there will be plenty to find out without that, once you get started.