To 後面何時需要加 ing?

to 係infinitive
eg. i want to eat an apple.
"eat"係不用加ing

而當to係以一個preposition用
eg. i look forward to talking with you.
"talk"就要用ing

呢d情況要知道個to係用來做preposition就加ing

使用ing需要既條件係:
1.一定要配搭be(is/am/are) 先可以加ing
2.係句子入面既意思係要"進行中"

e.g: I am watching TV now.
Look!The girl are running with the animals.

係入面, 我地見到 "...am watching..."同埋"Look!"
係現在進行式當中好重要既係睇詞語,
好似係 now Look! Listening! 等等既詞語
但係仲有D句子入面無呢D提示語, 所以要靠成句既解釋推斷係吾係用"ing"

2008-08-27 11:04:34 補充：
都吾記得答你問題
我地都知道係"to"後面係吾駛係個verb到加任何野
用番波波橙個句 am looking forward to SEEING you soon
佢既意思係搵時間去睇你個仔...個seeing即係指將來佢會做

佢既意思層面係帶到去將來

ing即做緊既意思 , 將個動詞後面加ing即表示進行緊一樣野 . 如果你話to後加ing大概意思係to緊 , 即現在開緊工 , 但好多時唔會咁樣寫 , 咁樣寫法只係口語寫法 ..

那时所谓的BARE INFINITIVE,但有时是要加ING的,好像是:-
I am looking forward to SEEING you soon.就是要加ING的.