定语从句引导词省略怎样分清楚

一般后面肯定是“主语+谓语”或许+某个介词,如：
1 This is the little village (that) the mayor visited last week-------括号中的that完全可以省略.
2 This is the village (that) the mayor used to live in.-------括号中的that完全可以省略.
祝你新年快乐.