Understanding the major symbols and how they connect to the theme is extremely important in literary analysis. You must understand the major ideas the author is trying to get across. Consider the elements of the story. We have the lottery itself which happens every year in order to help the corn grow. We have the slip of paper with the black dot which symbolizes death of the lottery "winner." The stones, represent the callousness of the townspeople who are happy to continue the lottery, no matter how savage, solely based on tradition.
When you consider these elements, it becomes clear that the author is condemning the act of blindly following traditions. This could potentially connect to many ideas in life, such as religion, family ties, societal rules, governmental control, etc. If people continue to blindly follow tradition without considering that it may be hurting them more than helping, they may be their own downfall. Tessie herself was content to participate until it was her own head on the chopping block, even offering up her own daughter to better her chances of living.
Creating visual representations of the symbols along with the themes can help you to make connections with the text. What do these symbols represent and how can you show that?