Once you have bagged up your leaves, make sure to add a bit of water and soil before sealing them. For tonne bags, do the best you can to keep them damp and cover. You will be amazed at how much will fit in a tonne bag as long as you keep compacting it down, normally done by jumping into the bag and treading on the contents.
As for collecting the leaves, I use a garden vacuum, like the one pictured to the right. Mine is a Stihl blower with a suction attachment, fondly nicknamed the Stihl Bag Pipes. The advantage of using one of these is that it shreds the leaves somewhat so they start to breakdown quicker. Alternatively, and if the leaves are reasonably dry, one can use a lawnmower – provided it can be set to a high setting. This has the same effect as the vacuum in shredding the leaves. If you don’t have any of these tools at your disposal, you can always rely on the old fashioned method of using a spring tine rake and a pair of big hands to collect the leaves.