As far as 'to' is concerned, a comma will not precede the word; 'to' is used in two structures namely 1. as a preposition before a noun and 2. as an infinitive marker before a verb as in 'to' sing, 'to' play etc. In both situations placing a comma before 'to' will be a mistake .
However in the case of 'for', which can be also used both as a conjunction as well as a preposition. Look at this following example
I am confident I will get 700 plus in GMAT, for I have been preparing for a couple
...
However in the case of 'for', which can be also used both as a conjunction as well as a preposition. Look at this following example
I am confident I will get 700 plus in GMAT, for I have been preparing for a couple
...
