1)先行词是不定代词：

　　all,few,little,much,something,nothing,anything等.Allthatwehavetodoistopractiseeveryday.

　　2)先行词被序数词或形容词最高级所修饰.

　　ThefirstlessonthatIlearnedwillneverbeforgotten.

　　3)先行词被all,any,every,each,few,little,no,some,等修饰.

　　Ihavereadallthebook(that)yougaveme.

　　4)先行词被theonly,thevery,thesame,thelast修饰时.

　　HeistheonlypersonthatIwanttotalkto.

　　5)先行词既有人又有物时.

　　Theytalkedofthingsandpersonsthattheyrememberedintheschool.

　　先行词是表示地点时,要根据从句的谓语动词是及物的还是不及物的.如果是及物的就用that(which),否则用where.

　　Thisisthehousewherehelivedlastyear.

　　Thisisthehousethat(which)hevisitedlastyear.