Ok, so we were doing these at kickboxing last night. My elbows tend to point out to the sides rather than point backwards. Is this doing it wrong? Do I use more back muscles if I point my elbows to the side?

I (and cute trainer) says yes, it's wrong, your elbows have to point straight back and be close to your body, no pushing yourself away from the bench to make it easier (ask me how I know!)

I'm hopeless at tricep bench dips, but we carry on!

Oh I'd better practise like that then, since I am (bad) tricep dip QUEEN at kickboxing!

Yep, elbow position is KEY to doing tri's correctly. You need to keep them pulled in in order to target the triceps. And it's definitely harder that way!

When I first started doing tricep kickbacks, I tied my elbows to my waist belt-style. That stopped me from using other muscles.

That's a good idea, the guys at the gym already think I'm nuts!!!! It's really demoralising when cute instructor bobs up and down with the greatest of ease whilst I struggle along.

It's alright for him, he's only got 120lbs to heft up and down as compared to my 199lbs!

You will also want to make sure that you are not psuhing your shoulrders up to your ears, but rather keep them down and back for the whole movement.
They kill me, so I substitute with overhead press.