[一级解密]规则动词的过去式由“动词原形+-ed”构成，具体变化有：
1. 直接在词尾加-ed。如: want—wanted, work—worked, need—needed, clean—cleaned
2. 以不发音的e结尾的在词尾加-d。如：like—liked, live—lived, use—used, move—moved
3. 以一个元音字母加一个辅音字母结尾的重读闭音节动词，先双写结尾的辅音字母，再加-ed。如：stop—stopped, trip—tripped
4. 以辅音字母加y结尾的动词，先把y变成i，再加-ed。如：study—studied, carry—carried, hurry—hurried, marry—married
[二级解密]规则动词词尾加-ed有三种读音：
1. 在清辅音后读作[t]。如：asked, helped, watched, stopped
2. 在浊辅音和元音后读作[d]。如：enjoyed, studied, moved, called
3. 在t / d后读作[id]。如：wanted, needed
[三级解密]不规则动词的过去式见课本后的不规则动词表。大体上归纳有以下六条记忆法：
1. 以t结尾的词，过去式与原形相同。如：put—put, let—let, cut—cut, beat—beat
2. 以d结尾的词，把d变成t。如:build—built, lend—lent, send—sent, spend—spent
3. 以n结尾的词，在词后加t。如：mean—meant, burn—burnt, learn—learnt
4. 以ow / aw结尾的词，把ow / aw变成ew。如：blow—blew, draw—drew, know—knew, grow—grew
5. 含有双写字母的词，将双写改为单写，在词尾加t。如：keep—kept, sleep—slept, feel—felt, smell—smelt
6. 含有元音字母o / i的词，将o / i变成a。如：sing—sang, give—gave, sit—sat, drink—drank
