It is best to purchase at least one guidebook. These are excellent. "Your Swedish Roots" is easier to start with and "Cradled in Sweden" is more detailed. I own both. The book titles below the images are links.
"Your Swedish Roots"
"Cradled in Sweden"
If you think about purchasing a used copy of "Cradled in Sweden", only purchase the 1995 and 2002 editions. The earlier editions have much less material. The two recommended editions have the same material, except the covers and type are different. (The author died between the two editions.)
You can also download a booklet with an overview of Swedish genealogy plus ideas on how to gather clues about where your ancestors may have lived in Sweden. This booklet is called "Tracing Your Swedish Ancestry" and was written by James E. Erickson and Nils William Olsson.
"Tracing Your Swedish Ancestry"
That last url changes frequently. It works today but if it changes, do what I do. Google the title. I have been able to find the site through many url changes by remembering the title.