More than often, when I make biscuits or pastries in the oven, no matter how much oil I grease the foil or?

Try parchment paper or silicone baking sheets. (You don't even have to clean the pan!)

Use Silpat baking mats, NOTHING sticks - http://www.silpat.com/

Depending on what you're cooking (biscuits like Southern US biscuits or UK biscuits a.k.a. cookies?) too much oil might be "frying" the items and causing them to stick or there are ingredients turning into caramel and melting onto the tray/foil. Have you tried not greasing the foil, or rubbing a very thin, light layer of butter (maybe even with a follow-up layer of flour?)

I used to have trouble with lace cookies sticking but solved it with silpat.

simple dont use the foil grease the baking tray with olive oil put biscuits directly onto it and you will have complete non stick biscuits try good luck,

Parchment Paper.

Simple, use parchment paper! No, flour, no grease, no sticking or burning. When I discovered it I proclaimed it a miracle.

silpats=silicone baking mats are the best! nothing ever sticks to them and they are reusable, if you don't want to purchase those use parchment paper.

grease the tin then shake a thin layer of flour on it

use baking paper or greaseproof paper.