Consigned to the compost
Start by pruning to the ground all the canes that produced fruit this season. They're usually pretty easy to spot as they still bear the remains of the fruits and flowers and will be starting to turn dry and yellow. Once these are out of the way, things become a little clearer.The plant will have already started to produce canes this year and these will be your fruit producers next summer. Retain the tallest and strongest looking ones. There will be shorter and thinner canes also, which you need to decide which to keep and which to prune out. Remove the really small ones and also anything that looks decidedly spindly. Weak looking canes will not produce fabulous berries. Focus too on allowing air to the lower stems and thin out canes where they're crowded.
Once that's done, give the plant a good water to rejuvenate it and keep to a regular (maybe weekly or fortnightly) feeding regime. The effort you put in now will pay off with next years' harvest.