Grammar問題

[To tell you the truth, I hate to do it]

樓主講得啱，to後面個 tell 字唔當係動詞。
[to tell] 係 infinitive。雖然 infinitive 係由 to + verb (simple form) 組成，但組成後便失去了 verb 的作用，而只用作 noun, adjective, 或 adverb。
[to tell you the truth] 是一個 infinitive phrase。整個短句 (即前半句) 用作一個助動詞 (adverb)，去形容下半句的動詞 (hate)。

[I want to go to school]

樓主又講得啱，want 係 main verb，go 唔係 main verb; go 係 infinitive [to go] 嘅一部份 。[to go] 嘅作用係助動詞, 去形容個main verb [want]。[to go to school] 係 infinitive phrase, 亦係 adverb，去形容個 main verb [want]。

2009-04-18 21:19:05 補充：
[To tell you the truth, I hate to do it]

前面半句是個助動詞短句 (adverb phrase)，又是 infinitive phrase，所以可以冇 main verb。
[To tell you the truth]，在這裏的作用就等於 [honestly]，是用來形容 hate 的狀態。
例如：
Honestly, I hate to do it.

不過，我也想過原句 係咪 [I can tell you the truth that I hate to do it] 嘅 short form。現正在 再做 research。

2009-04-18 21:23:26 補充：
忘記咗講一句一定要有 main verb， 但半句就唔駛都得。[to tell you the truth] 只係上半句。

tell 是動詞, 只不過 to 後面的動詞大多數都唔洗轉形態,即是唔 加任何ed,ing, s, es. 但不是全部e.g.I go to shopping. 而tell在句子中是動詞.
TO 後面可以跟人(noun)~I give a apple to you.
TO 後面可以跟(verb)~~I want to go to school