Couplings

Coupling help for beginner.

Having recently got into model railing after a gap since childhood (longer than I thought), I was bought a Hornby DCC Mixed Goods set for my birthday. The other day I purchased 2 Bachmann goods wagons (a firestone plank truck and a Toad Brake Van). All was well till I tried to couple up to a Loco. The couplings, although both use the same principle - hook and loop (tension lock?), they are completely different in size, and as a result create all sorts of derailments on bends and points, and uncouplings on the run.

I have read lots of forums talking about all sorts of different couplings, but that has just confused me more.

What options have I got?
What is the easiest and most cost effective method without destroying my existing rolling stock?

Other than that, DCC is great. I have also bought a Pendolino 4 car train which is great too.