We work it on a time and tip charge basis - however many hours we think it will take, at our standard hourly rate, plus vehicle cost, plus tip charges. And always overestimate - we've never yet been surprised by how little rubbish we've had to dispose of!
I charge my customers £48 per tonne of rubble/muck which i take to the local quarry and dispose of for free. Thats on top of any labour charges for actually loading the trailer.
Dont forget that you will require a waste carriers licence from your local council. Ive been reported twice in the last year but have had my licence to prove im allowed to carry and dispose of waste. Dont underestimate the underhand tactics of the competition!
I charge £1 per compost sized bag, £5 per bulk bag or about £50 per trailer of green waste. I get charged at my tip £50 per tonne with a minimum charge of £10 per drop. I fill the bags as much as possible, as much as one person can comfortably lift. All prices +VAT.
For heavy materials (soil, rubble) the tip charges £100 per tonne so it is usually more economical to hire a skip (£160 per 6yd3) or grab load (£300 per 14m3).
Some customers I include the waste in a fixed cost so I estimate what it will cost me in time to load waste, transport it, pay for it as well as wear and tear, fuel etc for vans and trailers.
I have a waste carrier licence as well and also need to factor in a bit of extra time to fill in waste transfer notes which customers usually say that they do not want or need (!)