I've dealt with this before and I consulted a traditional priest in doing so.
Usually you want to dispose of these items the way you would sacramentals since they bear the images of Our Lord etc., however there might be some exceptions depending on what exactly you have.
Things made of paper, thread/fabric, and wood can be reverently disposed of by burying, however it takes a while for these things to break down in soil, some longer than others. You're much better off just burning these.
Plastic objects should be burned and not buried since they don't decompose.
Liquids simply pour out on to soil and the container smashed or burn it if it's plastic.
Wax items won't break down. You'll have to burn them. If it's a candle remove the candle from the glass and burn it whole and smash the glass.
Glass and ceramics of course should be smashed. If you have something like a saint statue like this (and not made of wax or some other material), I'd personally be inclined to smash it anyway, the wholesomeness of the figure itself not withstanding, but I've never had to handle something like that (thankfully) so I can't bring myself to recommend doing that. Burying it however would not be sufficient because charms have to be destroyed to break their effects. Burying something like a ceramic is merely concealing it. Consult a priest on this one if you have something like this. Actually if you'd like, PM me and I'll try and get you in touch with a Traditional priest who I believe could help you with this.
Iron/steel objects can be slowly dissolved in vinegar.
Aluminum items can be melted but it takes a pretty hot fire to do it and a few logs in the hearth or BBQ won't cut it. If you can, find someone like a blacksmith who can melt them down for you.
This all might sound overkill, but that's more or less what I do with this stuff when it comes into my possession (pun unintended).