Summer fruiting raspberry canes (floricanes) make their fruit on stems that are one year old, as opposed to Autumn fruiting varieties (primocanes) that fruit on their new growth.
A summer fruiting raspberry cane only fruits once on each stem, so they should be cut down to ground level after harvesting.
Once you have removed the old canes, examine the remaining stems that began to grow that year: these will bear fruit the next year.
Select between four and eight of the biggest, strongest canes per plant and prune out all the others - this will encourage the plant to put most of its energy into making fruit.
Raspberries are best grown up a single post or on wires.
Raspberries often make suckers (shoots from roots some distance away from the main plant). If possible, dig down and tear them away from the root.
You can buy raspberry canes here.