下面的 to 是介词，后面可跟动词的 -ing 形式，一般不跟动词原形：

      look forward to, object to, be used to, prefer (doing one thing to doing another), get round to, in addition to (摘自《牛津英语用法指南》第四版104.2)

     下列动词后面接  to 时，这个 to 一定是动词不定式符号，即：下列动词后面可以接带 to 的动词不定式：

      afford, agree, appear, arrange, ask, attempt, can't bear, beg, begin, care, choose, consent, continue, dare, decide, expect, fail, forget, go on, happen, hate, help, hesitate, hope, intend, learn, like, love, manage, mean, neglect, offer, prefer, prepare, pretend, promise, propose, refuse, regret, remember, seem, start, swear, trouble, try, want, wish

 (摘自《牛津英语用法指南》第四版97节)