The question that prompted this: Finding descendants of Jamaican immigrant to England
We have several "I want to find the descendants of [name]" questions on the site, some of which have been closed as duplicates of this question. Finding descendants of British great grand uncle who emigrated to Australia?
The techniques for finding descendants may be the same for all localities, but the resources for each locality will differ. (Related question: Is the same question in a different geographical area a duplicate?)
I thought we had addressed this already with one good question on doing descendancy research, but I wasn't able to find it. I think we need a better Q/A as our model for closing Qs as duplicates instead of the one that just happened to be posted first.
To that end, I'm going to answer here with some links to resources to show what kinds of things I would include in a self-answered canonical question.
Note: We already have Contacting living distant relatives? on Contacting Living Relatives so the resources which address how to make contact belong in an answer over there.