Hey guy, you should give us the context or example because these rules depends on the specific context. I can give you example with two rule above.
We have to consider selling
the house. => -ing is role of NOUN
I'm used to playing
football => -ing form plays a role of Nound before preposition "to"
I look forward to reading
book. => -ing form plays a role of Nound before preposition "to"
If you can give your example and your choice, we will correct more specifically.
Hope that helps
Rules for posting in verbal gmat forum, read it before posting anything in verbal forum
Giving me + 1 kudos if my post is valuable with you
The more you like my post, the more you share to other's need
CR: Focus of the Week: Must be True Question