How do i get my 8 year old to stop sucking his tongue. he is starting to suck on objects?

Tongue or thumb?: If you meant thumb, normally a child outgrows this at a young age. The problem now is that at 8 years of age, his bite, appearance and speech may already be affected. See your dentist for an orthodontic consultation. If you did indeed mean your child is sucking his tongue then seek medical help.

Thumb more likely: I would gather you meant thumb sucking. Tongue sucking is possible but is less constant, as it is difficult to speak, eat or breathe while doing it. At 8 years of age thumb habits should be assessed by an orthodontist, likewise if you meant to say tongue thrusting (a particularly pernicious habit that can cause significant orthodontic problems). Best of luck.