1.动词作主语,开头,用doing
2. 介词 in/ at/ for/of /by / about/ with/ without / after/ before + doing
3. swimming club singing class
4.There be …doing (主动)
5. have trouble / problem / fun /…time doing
6. 感官动词 see / hear/ notice/ find / feel sb. doing (正在做)
7. practice doing finish doing enjoy doing mind doing spend…(in) doing stop doing(停止做) forget doing(忘了做过某事) remember doing (记得做过某事)